The Online Library of Liberty

A project of Liberty Fund, Inc.

• Introduction
• Textual Introduction
• Preface to the Third Edition[*]
• Chapter I: Introductory Remarks
• Chapter II: The Relativity of Human Knowledge
• Chapter III: The Doctrine of the Relativity of Human Knowledge, As Held By Sir William Hamilton
• Chapter IV: In What Respect Sir William Hamilton Really Differs From the Philosophers of the Absolute
• Chapter V: What Is Rejected As Knowledge By Sir William Hamilton, Brought Back Under the Name of Belief
• Chapter VI: The Philosophy of the Conditioned
• Chapter VII: The Philosophy of the Conditioned, As Applied By Mr. Mansel to the Limits of Religious Thought
• Chapter VIII: Of Consciousness, As Understood By Sir William Hamilton
• Chapter IX: Of the Interpretation of Consciousness
• Chapter X: Sir William Hamilton’s View of the Different Theories Respecting the Belief In an External World
• Chapter XI: The Psychological Theory of the Belief In an External World
• Chapter XII: The Psychological Theory of the Belief In Matter, How Far Applicable to Mind
• Chapter XIII: The Psychological Theory of the Primary Qualities of Matter
• Chapter XIV: How Sir William Hamilton and Mr. Mansel Dispose of the Law of Inseparable Association
• Chapter XV: Sir William Hamilton’s Doctrine of Unconscious Mental Modifications
• Chapter XVI: Sir William Hamilton’s Theory of Causation
• Chapter XVII: The Doctrine of Concepts, Or General Notions
• Chapter XVIII: Of Judgment
• Chapter XIX: Of Reasoning
• Chapter XX: On Sir William Hamilton’s Conception of Logic As a Science. Is Logic the Science of the Laws, Or Forms, of Thought?
• Chapter XXI: The Fundamental Laws of Thought According to Sir William Hamilton
• Chapter XXII: Of Sir William Hamilton’s Supposed Improvements In Formal Logic
• Chapter XXIII: Of Some Minor Peculiarities of Doctrine In Sir William Hamilton’s View of Formal Logic
• Chapter XXIV: Of Some Natural Prejudices Countenanced By Sir William Hamilton, and Some Fallacies Which He Considers Insoluble
• Chapter XXV: Sir William Hamilton’s Theory of Pleasure and Pain
• Chapter XXVI: On the Freedom of the Will
• Chapter XXVII: Sir William Hamilton’s Opinions On the Study of Mathematics
• Chapter XXVIII: Concluding Remarks
• Appendices
• Appendix A: Manuscript Fragments
• Appendix B: Textual Emendations
• Appendix C: Corrected References
• Appendix D: Bibliographic Index of Persons and Works Cited In the Examination, With Variants and Notes

CHAPTER XIII

The Psychological Theory of the Primary Qualities of Matter

for the reasons which have been set forth, I conceive Sir W. Hamilton to be wrong in his statement that a Self and a Not-self are immediately apprehended in our primitive consciousness. We have, in all probability, no notion of Not-self, until after considerable experience of the recurrence of sensations according to fixed laws, and in groups.^*aNor is it^a credible that the first sensation which we experience awakens in us any notion of an Ego or Self. To refer it to an Ego is to consider it as part of a series of states of consciousness, some portion of which is already past. The identification of a present state with a remembered state cognised as past, is what, to my thinking, constitutes the cognition that it is I who feel it. “I” means he who saw, touched, or felt something yesterday or the day before. No single sensation can suggest personal identity: this requires a series of sensations, thought of as forming a line of succession, and summed up in thought into a Unity.

But (however this may be) throughout the whole of our sensitive life except its first beginnings, we unquestionably refer our sensations to a me and a not-me. As soon as I have formed, on the one hand, the notion of Permanent Possibilities of Sensation, and on the other, of that continued series of feelings which I call my life, both these notions are, by an irresistible association, recalled by every sensation I have. They represent two things, with both of which the sensation of the moment, be it what it may, stands in relation, and I cannot be conscious of the sensation without being conscious of it as related to these two things. They have accordingly received relative names, expressive of the double relation in question. The thread of consciousness which I apprehend the sensation as a part of, is the subject of the sensation. The group of Permanent Possibilities of Sensation to which I refer it, and which is partially realized and actualized in it, is the object of the sensation. The sensation itself ought to have a correlative name; or rather, ought to have two such names, one denoting the sensation as opposed to its Subject, the other denoting it as opposed to its Object. But it is a remarkable fact, that this necessity has not been felt, and that the need of a correlative name to every relative one has been considered to be satisfied by the terms Object and Subject themselves; the object and the subject not being attended to in the relation which they respectively bear to the sensation, but being regarded as directly correlated with one another. It is true that they are related to one another, but only through the sensation: their relation to each other consists in the peculiar and different relation in which they severally stand to the sensation. We have no conception of either Subject or Object, either Mind or Matter, except as something to which we refer our sensations, and whatever other feelings we are conscious of. The very existence of them both, so far as cognisable by us, consists only in the relation they respectively bear to our states of feeling. Their relation to each other is only the relation between those two relations. The immediate correlatives are not the pair, Object, Subject, but the two pairs, Object, Sensation objectively considered; Subject, Sensation subjectively considered. The reason why this is overlooked, might easily be shown, and would furnish a good illustration of that important part of the Laws of Association which may be termed the Laws of Obliviscence.

I have next to speak of a psychological fact, also a consequence of the Laws of Association, and without a full appreciation of which, the idea of Matter can only be understood in its original groundwork, but not in the superstructure which the laws of our actual experience have raised upon it. There are certain of our sensations which we are accustomed principally to consider subjectively, and others which we are principally accustomed to consider objectively. In the case of the first, the relation in which we most frequently, most habitually, and therefore most easily consider them, is their relation to the series of feelings of which they form a part, and which, consolidated by thought into a single conception, is termed the Subject. In the case of the second, the relation in which we by preference contemplate them is their relation to some group, or some kind of group, of Permanent Possibilities of Sensation, the present existence of which is certified to us by the sensation we are at the moment feeling—and which is termed the Object. The difference between these two classes of our sensations, answers to the distinction made by the majority of philosophers between the Primary and the Secondary Qualities of Matter.

We can, of course, think of all or any of our sensations in relation to their Objects, that is, to the permanent groups of possibilities of sensation to which we mentally refer them. This is the main distinction between our sensations, and what we regard as our purely mental feelings. These we do not refer to any groups of Permanent Possibilities; and in regard to them the distinction of Subject and Object is merely nominal. These feelings have no Objects, except by metaphor. There is nothing but the feeling and its Subject. Metaphysicians are obliged to call the feeling itself the object. Our sensations, on the contrary, have all of them objects; they all are capable of being classed under some group of Permanent Possibilities, and being referred to the presence of that particular set of possibilities as the antecedent condition or cause of their own existence. There are, however, some of our sensations, in our consciousness of which the reference to their Object does not play so conspicuous and predominant a part as in others. This is particularly the case with sensations which are highly interesting to us on their own account, and on which we willingly dwell, or which by their intensity compel us to concentrate our attention on them. These are, of course, our pleasures and pains. In the case of these, our attention is naturally given in a greater degree to the sensations themselves, and only in a less degree to that whose existence they are marks of. And of the two conceptions to which they stand in relation, the one to which we have most tendency to refer them is the Subject; because our pleasures and pains are of no more importance as marks than any of our other sensations, but are of very much more importance than any others as parts of the thread of consciousness which constitutes our sentient life. Many indeed of our internal bodily pains we should hardly refer to an Object at all, were it not for the knowledge, late and slowly acquired, that they are always connected with a local organic disturbance, of which we have no present consciousness, and which is therefore a mere Possibility of Sensation. Those of our sensations, on the contrary, which are almost indifferent in themselves, our attention does not dwell on; our consciousness of them is too momentary to be distinct, and we pass on from them to the Permanent Possibilities of Sensation which they are the signs of, and which alone are important to us. We hardly notice the relation between these sensations and the subjective chain of consciousness of which they form so extremely insignificant a part: the sensation is hardly anything to us but the link which draws into our consciousness a group of Permanent Possibilities; this group is the only thing distinctly present to our thoughts. The unimpressive organic sensation merges in the mere mental suggestion, and we seem to cognise directly that which we think of only by association, and know only by inference. Sensation is in a manner blotted out, and Perception seems to be installed in its place. This truth is expressed, though not with sufficient distinctness, in a favourite doctrine of Sir W. Hamilton, that in the operations of our senses Sensation is greatest when Perception is least, and least when it is greatest; or, as he, by a very inaccurate use of mathematical language, expresses it, Sensation and Perception are in the inverse ratio of one another.

With regard to those sensations which, without being absolutely indifferent, are not, in any absorbing degree, painful or pleasurable, we habitually think of them only as connected with, or proceeding from, Objects. And I am disposed to believe, contrary to the opinion of many philosophers, that any of our senses, or at all events any combination of more than one sense, would have been sufficient to give us some idea of Matter. If we had only the senses of smell, taste, and hearing, but had the sensations according to fixed laws of coexistence so that whenever we had any one of them it marked to us a present possibility of having all the others, I am inclined to think that we should have formed the notion of groups of possibilities of sensation, and should have referred every particular sensation to one of these groups, which, in relation to all the sensations so referred to it, would have become an Object, and would have been invested in our thoughts with the permanency and externality which belong to Matter. But though we might, in this supposed case, have had an idea of Matter, that idea would necessarily have been of a very different complexion from what we now have. For, as we are actually constituted, our sensations of smell, taste, and hearing, and ^bas I believe (with the great majority of^b philosophers) those of sight also, are not grouped together directly, but through the connexion which they all have, by laws of coexistence or of causation, with the sensations which are referable to the sense of touch and to the muscles; those which answer to the terms Resistance, Extension, and Figure. These, therefore, become the leading and conspicuous elements in all the groups: where these are, the group is: every other member of the group presents itself to our thoughts, less as what it is in itself, than as a mark of these. As the entire group stands in the relation of Object to any one of the component sensations which is realized at a given moment, so do these special parts of the group become, in a manner, Object, in relation not only to actual sensations, but to all the remaining Possibilities of Sensation which the group includes. The Permanent Possibilities of sensations of touch and of the muscles, form a group within the group—a sort of inner nucleus, conceived as more fundamental than the rest, on which all the other possibilities of sensation included in the group seem to depend; these being regarded, in one point of view, as effects, of which that nucleus is the cause, in another as attributes, of which it is the substratum or substance. In this manner our conception of Matter comes ultimately to consist of Resistance, Extension, and Figure, together with miscellaneous powers of exciting other sensations. These three attributes become its essential constituents, and where these are not found, we hesitate to apply the name.

Of these properties, which are consequently termed the Primary Qualities of Matter, the most fundamental is Resistance: as is proved by numberous scientific controversies. When the question arises whether something which affects our senses in a peculiar way, as for instance whether Heat, or Light, or Electricity, is or is not Matter, what seems always to be meant is, does it offer any, however trifling, resistance to motion? If it were shown that it did, this would at once terminate all doubt. That Resistance is only another name for a sensation of our muscular frame, combined with one of touch, has been pointed out by many philosophers, and can scarcely any longer be questioned. When we contract the muscles of our arm, either by an exertion of will, or by an involuntary discharge of our spontaneous nervous activity, the contraction is accompanied by a state of sensation, which is different according as the locomotion consequent on the muscular contraction continues freely, or meets with an impediment. In the former case, the sensation is that of motion through empty space. After having had (let us suppose) this experience several times repeated, we suddenly have a different experience: the series of sensations accompanying the motion of our arm is brought, without intention or expectation on our part, to an abrupt close. This interruption would not, of itself, necessarily suggest the belief in an external obstacle. The hindrance might be in our organs; it might arise from paralysis, or simple loss of power through fatigue. But in either of these cases, the muscles would not have been contracted, and we should not have had the sensation which accompanies their contraction. We may have had the will to exert our muscular force, but the exertion has not taken place.^* If it does take place, and is accompanied by the usual muscular sensation, but the ^cdistinctive feeling which I have called the sensation of motion in empty space^c does not follow, we have what is called the feeling of Resistance, or in other words, of muscular ^daction^d impeded; and that feeling is the fundamental element in the notion of Matter which results from our common experience. But simultaneously with this feeling of Resistance, we have also feelings of touch; sensations of which the organs are not the nerves diffused through our muscles, but those which form a network under the skin; the sensations which are produced by passive contact with bodies, without muscular action. As these skin sensations of simple contact invariably accompany the muscular sensation of resistance—for we must touch the object before we can feel it resisting our pressure—there is early formed an inseparable association between them. Whenever we feel resistance we have first felt contact^e. Whenever^e we feel contact, we know that were we to exercise muscular action, we should feel more or less resistance. In this manner is formed the first fundamental group of Permanent Possibilities of Sensation; and as we in time recognise that all our other sensations are connected in point of fact with Permanent Possibilities of resistance—that in coexistence with them we should always, by sufficient search, encounter something which would give us the feeling of contact combined with the muscular sensation of resistance; our idea of Matter, as a Resisting Cause of miscellaneous sensations, is now constituted.

Let us observe, in passing, the elementary example here afforded of the Law of Inseparable Association, and the efficacy of that law to construct what, after it has been constructed, is undistinguishable, by any direct interrogation of consciousness, from an intuition. The sensation produced by the simple contact of an object with the skin, without any pressure—or even with pressure, but without any muscular reaction against it—is no more likely than a sensation of warmth or cold would be, to be spontaneously referred to any cause external to ourselves. But when the constant coexistence, in experience, of this sensation of contact with that of Resistance to our muscular effort whenever such effort is made, has erected the former sensation into a mark or sign of a Permanent Possibility of the latter; from that time forward, no sooner do we have the skin sensation which we call a sensation of contact, than we cognise, or, as we call it, perceive, something external, corresponding to the idea we now form of Matter as a resisting object. Our sensations of touch have become representative of the sensations of resistance with which they habitually coexist: just as philosophers have shown that the sensations of different shades of colour given by our sense of sight, and the muscular sensations accompanying the various movements of the eye, become representative of those sensations of touch and of the muscles of locomotion, which are the only real meaning of what we term the distance of a body from us.^*

The next of the primary qualities of Body is Extension; which has long been considered as one of the principal stumbling blocks of the Psychological Theory. Reid and Stewart were willing to let the whole question of the intuitive character of our knowledge of Matter, depend on the inability of psychologists to assign any origin to the idea of Extension, or analyse it into any combination of sensations and reminiscences of sensation. Sir W. Hamilton follows their example in laying great stress on this point.

The answer of the opposite school I will present in its latest and most improved form, as given by Professor Bain,^f in the First Part of his great work on the Mind.^†

Mr. Bain recognises two principal kinds or modes of discriminative sensibility in the muscular sense: the one corresponding to the degree of intensity of the muscular effort—the amount of energy put forth; the other corresponding to the duration—the longer or shorter continuance of the same effort. The first makes us acquainted with degrees of resistance: which we estimate by the intensity of the muscular energy required to overcome it. To the second we owe, in Mr. Bain’s opinion, our idea of Extension.

A theory of Extension somewhat similar, though less clearly unfolded, was advanced by Brown,^[*] and as it stands in his statement, fell under the criticism of Sir W. Hamilton; who gives it, as he thinks, a short and crushing refutation, as follows:

The dilemma looks formidable, but one of its horns is blunt; for the very assertion of Brown, and of all who hold the Psychological theory, is that the notion of length in space, not being in our consciousness originally, is constructed by the mind’s laws out of the notion of length in time. Their argument is not, as Sir W. Hamilton fancied, a fallacious confusion between two different meanings of the word lengthⁱ; they maintain the one to be a product of the otherⁱ . Sir W. Hamilton did not fully understand the argument. He saw that a succession of feelings, such as that which Brown spoke of, could not possibly give us the idea of simultaneous existence. But he was mistaken in supposing that Brown’s argument implied this absurdity. The notion of simultaneity must be supposed to have been already acquired; as it necessarily would be at the very earliest period, from the familiar fact that we often have sensations simultaneously. What Brown had to show was, that the idea of the particular mode of simultaneous existence called Extension, might arise, not certainly out of a mere succession of muscular sensations, but out of that added to the knowledge already possessed that sensations of touch may be simultaneous. Suppose two small bodies, A and B, sufficiently near together to admit of their being touched simultaneously, one with the right hand, the other with the left. Here are two tactual sensations which are simultaneous, just as a sensation of colour and one of odour might be; and this makes us cognise the two objects of touch as both existing at once. The question then is, what have we in our minds, when we represent to ourselves the relation between these two objects already known to be simultaneous, in the form of Extension, or intervening Space—a relation which we do not suppose to exist between the colour and the odour. Now those who agree with Brown, say that whatever the notion of Extension may be, we acquire it by passing our hand or some other organ of touch, in a longitudinal direction from A to B: that this process, as far as we are conscious of it, consists of a series of varied muscular sensations, differing according to the amount of muscular effort, and, the effort being given, differing in length of time. When we say that there is a space between A and B, we mean that some amount of these muscular sensations must intervene; and when we say that the space is greater or less, we mean that the series of sensations (amount of muscular effort being given) is longer or shorter. If another object, C, is farther off in the same line, we judge its distance to be greater, because to reach it, the series of muscular sensations must be further prolonged, or else there must be the increase of effort which corresponds to augmented velocity. Now this, which is ^jnot denied to be^j the mode in which we become ^kaware^k of extension, ^lby any other sense than sight,^l is considered by the psychologists in question to be extension. The idea of Extended Body they consider to be that of a variety of resisting points, existing simultaneously, but which can be perceived by the same tactile organ only successively, at the end of a series of muscular sensations which constitutes their ^mdistance^m ; and are said to be at different distances from one another because the series of intervening muscular sensations is longer in some cases than in others.^*

The theory may be recapitulated as follows. The sensation of muscular motion unimpeded constitutes our notion of empty space, and the sensation of muscular motion impeded constitutes that of filled space. Space is Room—room for movement; which its German name, Raum, distinctly confirms. We have a sensation which accompanies the free movement of our organs, say for instance of our arm. This sensation is variously modified by the direction, and by the amount of the movement. We have different states of muscular sensation corresponding to the movements of the arm upward, downward, to right, to left, or in any radius whatever of a sphere of which the joint, that the arm revolves round, forms the centre. We have also different states of muscular sensation according as the arm is moved more; whether this consists in its being moved with greater velocity, or with the same velocity during a longer time: and the equivalence of these two is speedily learnt, by ⁿfinding that a greater effort conducts the hand in a shorter time from the same point to the same point; from the tactual impression A to the tactual impression Bⁿ . These different kinds and qualities of muscular sensation, experienced in getting from one point to another (that is, obtaining in succession two sensations of touch and resistance, the objects of which are regarded as simultaneous) are all we mean by saying that the points are separated by spaces, that they are at different distances, and in different directions. An intervening series of muscular sensations before the one object can be reached from the other, is the only peculiarity which (according to this theory) distinguishes simultaneity in space, from the simultaneity which may exist between a taste and a colour, or a taste and a smell: and we have no reason for believing that Space or Extension in itself, is anything different from that which we recognise it by. It appears to me that this doctrine is sound, and that the muscular sensations in question are the sources of all the notion of Extension which we should ever obtain from the tactual and muscular senses without the assistance of the eye.

But the participation of the eye in generating our actual notion of Extension, very much alters its character, and is, I think, the main cause of the difficulty felt in believing that Extension derives its meaning to us from a phænomenon which is not synchronous but successive. The fact is, that the conception we now have of Extension or Space is an eye picture, and comprehends a great number of parts of Extension at once, or in a succession so rapid that our consciousness confounds it with simultaneity. How, then (it is naturally asked) can this vast collection of consciousnesses which are sensibly simultaneous, be generated by the mind out of its consciousness of a succession—the succession of muscular feelings? An experiment may be conceived, which would throw great light on this subject, but which unfortunately is more easily imagined than obtained. There have been persons born blind who were mathematicians, and I believe even naturalists; and it is not impossible that one day a person born blind may be a metaphysician. The first who is so, will be able to enlighten us on this point. For he will be an experimentum crucis^[*] on the mode in which extension is conceived and known, independently of the eye. Not having the assistance of that organ, a person blind from birth must necessarily perceive the parts of extension—the parts of a line, of a surface, or of a solid—in conscious succession. He perceives them by passing his hand along them, if small, or by walking over them if great. The parts of extension which it is possible for him to perceive simultaneously, are only very small parts, almost the minima of extension. Hence, if the Psychological theory of the idea of extension is true, the blind metaphysician would feel very little of the difficulty which seeing metaphysicians feel, in admitting that the idea of Space is, at bottom, one of time—and that the notion of extension or distance, is that of a motion of the muscles continued for a longer or a shorter duration. If this analysis of extension appeared as paradoxical to the metaphysician born blind, as it does to Sir W. Hamilton, this would be a strong argument against the Psychological theory. But if, on the contrary, it did not at all startle him, that theory would be very strikingly corroborated.

We have no experiment directly in point. But we have one which is the very next thing to it. We have not the perceptions and feelings of a metaphysician blind from birth, told and interpreted by himself. But we have those of an ordinary person blind from birth, told and interpreted for him by a metaphysician. And the English reader is indebted for them to Sir W. Hamilton. Platner, “a man no less celebrated as an acute philosopher than as a learned physician and an elegant scholar,”^[*] endeavoured to ascertain by observation what notion of extension was possessed by a person born blind, and made known the result in words which Sir W. Hamilton has rendered into his clear English.

The highly instructive representation here given by Platner, of this person’s state of mind, is exactly that which we have just read in Mr. Bain, and which that philosopher holds to be the primitive conception of extension by all of us, before the wonderful power of sight and its associations, in abridging the mental processes, has come into play. The conclusion which, as we have seen, Platner draws from the case, is that we obtain the idea of extension solely from sight; and even Sir W. Hamilton is staggered in his belief of the contrary. But Platner, though unintentionally, puts a false colour on the matter when he says that his patient had no perception of extension. He used the terms expressive of it with such propriety and discrimination, that Platner, by his own account, did not at first suspect him of not meaning by those terms all that is meant by persons who can see. He therefore meant something; he had impressions which the words expressed to his mind; he had conceptions of extension, after his own manner. But his idea of degrees of extension was but the idea of a greater or smaller number of sensations experienced in succession “to attain from some one feeling to another;” that is, it was exactly what, according to Brown’s and Mr. Bain’s theory, it ought to have been. And, the sense of touch and of the muscles not being aided by sight, the sensations continued to be conceived by him only as successive: his mental representation of them remained a conception of a series, not of a coexistent group. Though he must have had experience of simultaneity, for no being who has a plurality of senses can be without it, he does not seem to have thoroughly realized the conception of the parts of space as simultaneous. Since what was thus wanting to him, is the principal feature of the conception as it is in us, he seemed to Platner to have no notion of extension. But Platner, fortunately, being a man who could both observe, and express his observations precisely, has been able to convey to our minds the conception which his patient really had of extension; and we find that it was the same as our own, with the exception of the element which, if the Psychological theory be true, was certain to be added to it by the sense of sight. For, when this sense is awakened, and its sensations of colour have become representative of the tactual and muscular sensations with which they are coexistent, the fact that we can receive a vast number of sensations of colour at the same instant (or what appears such to our consciousness) puts us in the same position as if we had been able to receive that number of tactual and muscular sensations in a single instant. The ideas of all the successive tactual and muscular feelings which accompany the passage of the hand over the whole of the coloured surface, are made to flash on the mind at once: and impressions which were successive in sensation become coexistent in thought. From that time we do with perfect facility, and are even compelled to do, what Platner’s patient never completely succeeded in doing, namely, to think all the parts of extension as coexisting, and to believe that we perceive them as such. And if the laws of inseparable association, which are already admitted as the basis of other acquired perceptions of sight, are considered in their application to this case, it is certain that this apparent perception of successive elements as simultaneous ^owould^o be generated and would supply all that there is in our idea of extension, more than there was in that of Platner’s patient.^*

I shall quote, in continuation, part of the exposition by Mr. Bain, of the machinery by which our consciousness of Extension becomes an appendage of our sensations of Sight. It is a striking example of the commanding influence of that sense; which, though it has no greater variety of original impressions than our other special senses, yet owing to the two properties, of being able to receive a great number of its impressions at once, and to receive them from all distances, takes the lead altogether from the sense of touch: and is not only the organ by which we read countless possibilities of tactual and muscular sensations which can never, to us, become realities, but substitutes itself for our touch and our muscles even where we can use them—causes their actual use as avenues to knowledge, to become, in many cases, obsolete,—the sensations themselves to be little heeded and very indistinctly remembered,—and communicates its own prerogative of simultaneousness to impressions and conceptions originating in other senses, which it could never have given, but only suggests, through visible marks associated with them by experience.

“The distinctive impressibility of the eye,” says Mr. Bain,

These slight changes in the action of the muscles that move the eye, habitually effected in a time too short for computation, are the means by which our visual impressions from the whole of that portion of the universe which is visible from the position where we stand, may be concentrated within an interval of time so small that we are scarcely conscious of any interval; and they are, in my apprehension, the generating cause of all that we have in our notion of extension over and above what Platner’s patient had in his. He had to conceive two or any number of bodies (or resisting objects) with a long train of sensations of muscular contraction filling up the interval between them: while we, on the contrary, think of them as rushing upon our sight, many of them at the same instant, all of them at what is scarcely distinguishable from the same instant; and this visual imagery effaces from our minds any distinct consciousness of the series of muscular sensations of which it has become representative. The simultaneous visual sensations are to us symbols of tactual and muscular ones which were slowly successive.

This last extract is from Mr. Herbert Spencer,^* whose Principles of Psychology, in spite of some doctrines which he holds in common with the intuitive school, are on the whole one of the finest examples we possess of the Psychological Method in its full power. His treatment of this subject, and Mr. Bain’s, are at once corroborative and supplementary of one another: and to them I must refer the reader who desires an ampler elucidation of the general question. The remainder of this chapter will be devoted to the examination of some peculiarities in Sir W. Hamilton’s treatment of it.

Sir W. Hamilton relies mainly upon one argument to prove that Vision, without the aid of Touch, gives an immediate knowledge of Extension: which argument had been anticipated in a passage which he quotes from D’Alembert.^† The following is his own statement of it.

And farther on:

I must acknowledge that I cannot make the answer to this argument as thorough and conclusive as I could wish; for we have not the power of making an experiment, the completing converse of Platner’s. There is no example of a person born with the sense of sight, but without those of touch and the muscles: and nothing less than this would enable us to define precisely the extent and limits of the conceptions which sight is capable of giving, ^qindependently^q of association with impressions of another sense. There are, however, considerations well adapted to moderate the extreme confidence which Sir W. Hamilton places in this argument. First, it must be observed that when the eye, at present, takes cognizance of ^ra^r visible figure, it does not cognise it by means of colour alone, but by all those motions and modifications of the muscles connected with the eye, which have so great a share in giving us our acquired perceptions of sight. To determine what can be cognised by sight alone, we must suppose an eye incapable of these changes; which can neither have the curvature of its lenses modified nor the direction of its axis changed by any mode of muscular action; which cannot, therefore, travel along the boundary line that separates two colours, but must remain fixed with a steady gaze on a definite spot. If we once allow the eye to follow the direction of a line or the periphery of a figure, we have no longer merely sight, but important muscular sensations superadded. Now there is nothing more certain than that an eye with its axis immovably fixed in one direction, gives a full and clear vision of but a small portion of space, that to which the axis directly points, and only a faint and indistinct one of the other points surrounding it. When we are able to see any considerable portion of a surface so as to form a distinct idea of it, we do so by passing the eye over and about it, changing slightly the direction of the axis many times in a second. When the eye is pointed directly to one spot, the faint perceptions we have of others are barely sufficient to serve as indications for directing the axis of the eye to each of them in turn, when withdrawn from the first. Physiologists have explained this by the fact, that the centre of the retina is furnished with a prodigiously greater number of nervous papillæ, much finer and more delicate individually, and crowded closer together, than any other part. Whatever be its explanation, the fact itself is indubitable; and seems to warrant the conclusion that if the axis of the eye were immovable, and we were without the muscular sensations which accompany and guide its movement, the impression we should have of a boundary between two colours would be so vague and indistinct as to be merely rudimentary.

A rudimentary conception must be allowed, for it is evident that even without moving the eye we are capable of having two sensations of colour at once, and that the boundary which separates the colours must give some specific affection of sight, otherwise we should have no discriminative impressions capable of afterwards becoming, by association, representative of the cognitions of lines and figures which we owe to the tactual and the muscular sense. But to confer on these discriminative impressions the name which denotes our matured and perfected cognition of Extension, or even to assume that they have in their nature anything in common with it, seems to be going beyond the evidence. ^sBerkeley acknowledged a very considerable amount of perception by the eye alone, of something which it was possible to call by the name of extension; and that which is so perceived has, since his time, been known to philosophers as Visible Extension, in contradistinction to Tangible.^[*] But Berkeley maintained that Visible Extension not only is not the same thing as Tangible Extension, but has not the smallest likeness to it, and that a person born with only one of the two senses, and afterwards acquiring the other, would, until there had been time to learn their mutual relation by experience, never suspect that there was any connexion between them.^[†] In point of fact, those who are born blind and afterwards acquire sight, know by the information of others that the eye pictures and the tactual sensations come from the same objects: yet even with that help it is always a work of time and difficulty to connect the one with the other.^s Sir W. Hamilton appears to think that extension as revealed by the eye, is identical with the extension which we know by touch, except that it is only in two dimensions. “It is not,” he says, “all kind of extension and form that is attributed to sight. It is not figured extension in all the three dimensions, but only extension as involved in plane figures; that is, only length and breadth.”^* But to have the notion of extension even in length and breadth as we have it, is to have it in such a manner that we might know certain muscular facts without having tried: as, for instance, that if we placed our finger on the spot corresponding to one end of a line, or boundary of a surface, we should have to go through a muscular motion before we could place it on the other. Is there the smallest reason to suppose that on the evidence of sight alone, we could arrive at this conclusion in anticipation of the sense of touch? I cannot admit that we could have what is meant by a perception of superficial space, unless we conceived it as something which the hand could be moved across; and, whatever may be the retinal impression conveyed by the line which bounds two colours, I see no ground for thinking that by the eye alone we could acquire the conception of what we now mean when we say that one of the colours is outside the other.^* On this point I may again quote Mr. Bain.

Sir W. Hamilton does not limit the perception of Extension to sight and touch, either separately or combined with one another. “The opinions,” he says,

It may safely be admitted that whenever we are conscious of two sensations as “one out of another,” in the sense of locality, we have a perception of space; for the two expressions are equivalent. But to have a consciousness of difference between two sensations which are felt simultaneously, is not to feel them as “one out of another” in this sense; and the very question to be decided is, whether any of our senses, apart from feelings of muscular motion, gives us the notion of “one out of another” in the sense necessary to support the idea of Extension.

Sir W. Hamilton thinks that whenever two different nervous filaments are simultaneously affected at their extremities, the sensations received through them are felt as one out of the other. It is extremely probable that the affection of two distinct nervous filaments is the condition of the discriminative sensibility which furnishes us with sensations capable of becoming representative of objects one out of the other. But that is a different thing from giving us the perception directly. Undoubtedly we recognise difference of place in the objects which affect our senses, whenever we are aware that those objects affect different parts of our organism. But when we are aware of this, we already have the notion of Place. We must be aware of the different parts of our body as one out of another, before we can use this knowledge as a means of cognising a similar fact in regard to other material objects. This Sir W. Hamilton admits; and what, therefore, he is bound to prove is, that the very first time we received an impression of touch, or of any other sense, affecting more than one nervous filament, we were conscious of being affected in a plurality of places. This he does not even attempt to do; and direct proof is palpably unattainable. As a matter of indirect evidence, we may oppose to this theory Mr. Bain’s, according to which, apart from association, we should not have any impression of ^xthis^x kind, and should in general be conscious only of a greater mass or “volume”^[*] of sensation when we were affected in two places, than when only in one; like the more massive sensation of heat which we feel when our bodies are immersed in a warm bath, compared with that which we feel when heat of the same, or even of greater intensity, is applied only to our hands or feet. Mr. Bain’s doctrine, being as consistent with the admitted facts of the case as Sir W. Hamilton’s, has a good claim, on his own law of Parcimony, to be preferred to it. But, besides, there are recorded facts which agree with Mr. Bain’s theory, and are quite irreconcilable with Sir W. Hamilton’s; and to find such we need not travel beyond Sir W. Hamilton’s own pages.

One of them is the very case we have already had before us, that recorded by Platner. The facts of this case are quite inconsistent with the opinion, that we have a direct perception of extension when an object touches us in more than one place, including the extremities of more than one nervous filament. Platner expressly says that his patient, when an object touched a considerable part of the surface of his body, but without exciting more than one kind of sensation, was conscious of no local difference—no “outness” of one part of the sensation in relation to another part—but only (we may presume) of a greater quantity of sensation; as Mr. Bain would call it, a greater ^yvolume^y . As Platner expresses it, “if objects and the parts of his body touched by them, did not make different kinds of impression on his nerves of sensation, he would take everything external for one and the same. In his own body, he absolutely did not discriminate head and foot at all by their distance, but merely by the difference of the feelings.”^[*] Such an experiment, reported by a competent observer, is of itself almost enough to overthrow Sir W. Hamilton’s theory.

In like manner, the patient in Cheselden’s celebrated case, after his second eye was couched, described himself as seeing objects twice as large with both eyes as with one only;^[†] that is, he had a double quantity, or double volume of sensation, which suggested to his mind the idea of a double size.^*

Another case, for the knowledge of which I am also indebted to Sir W. Hamilton—who knew it through an abstract given by M. Maine de Biran^[*] of the original report “by M. Rey Régis, a medical observer, in his Histoire naturelle de l’âme”^[†] —is as incompatible with Sir W. Hamilton’s theory as Platner’s case. It is the case of a patient who lost the power of movement in one-half of his body, apparently from temporary paralysis of the motory nerves, while the functions of the sensory nerves seemed unimpaired. This patient, it was found, had lost the power of localizing his sensations.

It would be premature to establish a scientific inference upon a single experiment: but if confirmed by repetition, this is an experimentum crucis.^[‡] So far as one experiment can avail, it^a proves, that sensation without motion does not give the perception of difference of place in our bodily organs (not to speak of outward objects), and that this perception is even now entirely an inference, dependent on the muscular feelings.^†

It gives a very favourable idea of Sir W. Hamilton’s sincerity and devotion to truth, that he should have drawn from their obscurity, and made generally known, two cases which make such havoc with his own opinions as this and Platner’s; for though he did not believe the cases to be really inconsistent with his theory, he can hardly have been entirely unaware that they could be used against it.

The only other point in Sir W. Hamilton’s doctrines respecting the Primary Qualities which it is of importance to notice, is one, I believe, peculiar to himself, and certainly not common to him with any of his eminent predecessors in the same school of thought. It is the doctrine, that those qualities are not perceived—are not directly and immediately cognized—in things external to our bodies, but only in our bodies themselves. “A Perception,” he says,

Neither, according to him, do we perceive, or immediately know, “extension in its true and absolute magnitude;” our perceptions giving different impressions of magnitude from the same object, when placed in contact with different parts of our body.

Thus, according to Sir W. Hamilton, all our cognitions of extension and figure in anything except our own body, and of the real amount of extension even in that, are not perceptions, or states of direct consciousness, but “inferences,” and even inferences “by observation and induction” from our experience. Now, we know how contemptuous he is of Brown, and other “Cosmothetic Idealists,” for maintaining that the existence of extension or extended objects otherwise than as an affection of our own minds, is not a direct perception but an inference. We know how he reproaches this opinion with being subversive of our Natural Beliefs; how often he repeats that the testimony of consciousness must be accepted entire, or not accepted at all; how earnestly and in how many places he maintains

All this, it appears, is only true of the extension of our own bodies. The extension of any other body is not known immediately or by perception, but as an inference from the former. I ask any one, whether this opinion does not contradict our “natural beliefs” as much as any opinion of the Cosmothetic Idealists can do; whether to the natural, or non-metaphysical man, it is not as great a paradox to affirm that we do not perceive extension in anything external to our bodies, as that we do not perceive extension in anything external to our minds; and whether, if the natural man can be brought to assent to the former, he will find any additional strangeness or apparent absurdity in the latter. This is only one of the many instances in which the philosopher who so vehemently accuses other thinkers of affirming the absolute authority of Consciousness when it is on their own side, and rejecting it when it is not, lays himself open to a similar charge. The truth is, it is a charge from which no psychologist, not Reid himself, is exempt. No person of competent understanding has ever applied himself to the study of the human mind, and not discovered that some of the common opinions of mankind respecting their mental consciousness are false, and that some notions, apparently intuitive, are really acquired. Every psychologist draws the line where he thinks it can be drawn most truly. Of course it is possible that Sir W. Hamilton has drawn it in the right place, and Brown in the wrong. Sir W. Hamilton would say that the common opinions which he contests are not Natural Beliefs, though mistaken for such. And Brown thinks exactly the same of those which are repugnant to his own doctrine. Neither of ^bthem^b can justify himself but by pointing out a mode in which the apparent perceptions, supposed to be original, may have been acquired; and neither can charge the other with anything worse than having made a mistake in this extremely delicate process of psychological analysis. Neither of them has a right to give to a mistake in such a matter, the name of a rejection of the testimony of consciousness, and attempt to bring down the other by an argument which is of no possible value except ad invidiam, and which in its invidious sense is applicable to them both, and to all psychologists deserving the name.

A host of critics, headed by Dr. M‘Cosh, Mr. Mahaffy, and the writer in Blackwood [W. H. Smith], have directed their shafts against this chapter; but Professor Fraser, himself a host, is on my side. [See “Berkeley’s Theory of Vision,” pp. 202, 218n.] The essential point in the controversy being the analysis of Extension, I shall confine my notice to the arguments bearing upon that point.

This orderly and succinct mode of setting forth the objection is a great convenience for answering it. I shall take Mr. Mahaffy’s points in his own order.

(α) The phraseology employed to express the data common to both parties must, at least in the commencement, be that which common language affords; since no other would enable the reader to understand, without a laborious process, on a subject already so difficult, what are the facts meant. But the phraseology, of course, must not be so used as to assume anything which either the theory itself, or the theory opposed to it, does not admit. As Mr. Mahaffy observes, “such expressions as the range of a limb, or the sweep of a limb,” must “be carefully confined to the mere succession of feelings in moving it.” And if the reader turns back to the first of the quoted passages, he will find that Mr. Bain has been most industrious in directing attention to the feelings involved in the motion of a limb, as the point to be attended to, in contradistinction to the motion itself, and in showing that his expressions are to be understood of the former, and not of the latter.

(γ) Velocity or rapidity, comparison of quicker and slower motions, must not, Mr. Mahaffy says, be postulated, because quicker or slower have no meaning but with reference to the greater or smaller space traversed in a given time. It is true that the two motions derive their name from space; but are the motions themselves therefore undistinguishable? A saw and a hatchet are so called on account of the different kind of work they do; but can we not also distinguish the two objects when we see them? Again I say, what is postulated is not the space traversed, but the greater or less energy of the muscular sensation. It only remains to be explained how we learn that a more energetic sensation lasting a shorter time, is equivalent to a less energy continued for a longer time. Mr. Bain thinks we learn this by their both producing the same effect in “exhausting the full range of the limb;” by which he means, attaining the extreme limit of the sensation which accompanies protension—the point beyond which no further addition to it can be made. Where is the petitio principii here? I think that the solution is an admissible one—that we may fairly be supposed to take the entire series of the sensations which accompany the stretching out of the limb, as a unit of measurement, divisible into an ascending scale of degrees, which may be passed through in a shorter or a longer time, but the sum of which is always equal to itself. I have myself pointed out another road by which we might arrive at the same equivalence. We have two simultaneous sensations of touch with our two hands. We then move the right hand until it joins the left, and touches the same object. It need not be supposed that we yet know them as our hands, or the object as a body, or know of our right hand as moving through space. But the two simultaneous sensations of touch, either of which we may prolong or repeat at pleasure, have given us the notion of a permanent element in touch, and of two such permanent elements as coexisting. We have now had the two sensations of touch with a single hand, but separated by a series of the sensations accompanying muscular movement: and we find that to get from one of the tactual sensations to the other requires a shorter time, in proportion to the energy of the intervening muscular sensations. In this mental process time is postulated, but not space: and it is contended that the shorter time, or its equivalent, the greater energy, required to get from one object of touch to another already recognised as simultaneous, is the measure, in the last resort, of their distance in space. The eye then comes in, and with its greater powers of simultaneous sensation, it gathers up, by its acquired perceptions, a host of such measurements in one apparent intuition.

According to Dr. M‘Cosh, the reference of sensations to a lost limb contradicts not his but the association theory; since the lapse of years after the loss of the limb would be sufficient to destroy the old association. [Ibid., p. 351.] And this, in the great majority of cases, it probably does. But it is a frequent experience that a sensation exactly like one we have formerly felt, and like nothing else, revives even after many years a long forgotten remembrance. Again, Dr. M‘Cosh says that in the case of the new nose, the affection, according to the association theory, “should have been felt in the forehead, not till the isthmus was cut, but till the old association was gone; and this,” according to me, “might not have been for twenty years.” [Ibid.] This overlooks an important feature in the case. When not only the old nervous connexion has been cut off, but a new one formed, between the new nose and the nervous trunk which connected the old nose with the brain, the sensations become identical with those which were referred to the old nose when it existed; and the reference of them to the nose is thus supported by as old and strong an association as the previous reference of them to the forehead: with the difference that while every day helps to dissolve the one association, every day strengthens and rivets the other.

I believe I have noticed every plausible objection to Mr. Bain’s and my own analysis of Extension, which has a sufficiently individual character to require an answer by itself. The subject is in need of further study before all its obscure corners will be completely lighted up; but this it can hardly fail to receive, now that highly competent thinkers are engaged in extending our knowledge of the Mind by the application of the Psychological Method, grounded on the Laws of Association.^c

[* ][67] In the first edition I said: “But without the notion of not-self, we cannot have that of self, which is contrasted with it.” [Seea-a below.] In saying this I overlooked the fact, that my own sensations and other feelings, as distinguished from what I call Myself, are a sufficient Not-self to make the Self apprehensible. The contrast necessary to all cognition is sufficiently provided for by the antithesis between the Ego and particular modifications of the Ego.

[a-a]651, 652 But without the notion of not-self, we cannot have that of self which is contrasted with it: and independently of this, it is not

[b-b]651, 652 (as I believe, with nearly all

[* ]Sir W. Hamilton thinks that we are conscious of resistance through a “mental effort or nisus to move,” distinct both from the original will to move, and from the muscular sensation: “for we are,” he says, “conscious of it, though, by a narcosis or stupor of the sensitive nerves we lose all feeling of the movement of the limb; though by a paralysis of the motive nerves no movement of the limb follows the mental effort to move; though by an abnormal stimulus of the muscular fibres, a contraction in them is caused even in opposition to our will.” (“Dissertations on Reid,” [Note D,] pp. 864n-5n.) If all this is true—though by what experiments it has been substantiated we are not told—it does not by any means show that there is a mental nisus not physical, but merely removes the seat of the nisus from the nerves to the brain.

[c-c]651, 652 expected sensation of locomotion

[d-d]651, 652 motion

[e-e]651, 652 ; whenever

[* ]Sir W. Hamilton draws a distinction between two kinds of resistance, or rather, between two senses of the word: the one, that which I have mentioned, and which is a sensation of our muscular frame; the other, the property of Matter which the old writers called Impenetrability, being that by which, however capable of being compressed into a smaller space, it refuses to part with all its extension, and be extruded from space altogether. [See “Dissertations,” Note D, pp. 849, 851-2.] But these two kinds of resistance are merely two modes of regarding and naming the same state of consciousness; for if the body could be pressed entirely out of space, the only way in which we should discover that it had vanished would be by the sudden cessation of all sensations of resistance. It is always the muscular sensation which constitutes the presence, and its negation the absence, of body, in any given portion of space.

[f]651, 652, 67 of Aberdeen,

[† ]The Senses and the Intellect [London: Parker, 1855], pp. 113-17. My first extract is from the original edition; for in the one recently published (and enriched by many valuable improvements) the exposition I now quote is given more summarily, and in a manner otherwise less suited for my purpose. [2nd ed. (London: Longman, Green, Longman, Roberts, and Green, 1864), pp. 111-15.]

gDr. M‘Cosh, without any warrant, speaks of Mr. Bain as having “elaborated into a minute system the general statements scattered throughout Mr. Mill’s Logic” ([Examination,] p. 121); and in another passage refers to him and to Mr. Herbert Spencer (Mr. Herbert Spencer!) as merely following out an investigation indicated by me. (Ibid., pp. 123-4.) Coleridge reminded one of his critics, that there are such things in the world as springs, and that the water a man draws does not necessarily come from a hole made in another man’s cistern. [“Preface to Christabel,” in Christabel; Kubla Khan, a Vision; The Pains of Sleep (London: Murray, 1816), p. vi.] Mr. Bain did not stand in need of any predecessor except our common precursors, and has taught much more to me, on these subjects, than there is any reasonable probability that I can have taught to him. Dr. M‘Cosh falls into a corresponding mistake concerning myself, when he ascribes my regarding it “as impossible for the mind to rise to first or final causes, or to know the nature of things,” to “the influence” of M. Comte. (Examination, pp. 7-8.) The larger half of my System of Logic, including all its fundamental doctrines, was written before I had even seen the Cours de Philosophie Positive. That work was indebted to M. Comte for many valuable thoughts, but a short list would exhaust the chapters, and even the pages, which contain them. [See the Textual Introduction to System of Logic, Collected Works, Vol. VII, pp. lxxviii, lxxxii-lxxxiii, and xc-xci.] As for the general doctrine which Dr. M‘Cosh’s words so imperfectly express—that our knowledge is only of the coexistences and sequences, or the similitudes, of phænomena; I was familiar with it before I was out of boyhood from the teachings of my father, who had learnt it where M. Comte learnt it—from the methods of physical science, and the writings of their philosophical predecessors. Ever since the days of Hume, that doctrine has been the general property of the philosophic world. From the time of Brown it has entered even into popular philosophy.ghI have given a brief history of it in Auguste Comte and Positivism.h [See Collected Works, Vol. X, pp. 265-9.]

[[*] ]See Lectures, Vol. I, pp. 524-48, and Vol. II, pp. 1-22.

[* ]“Dissertations on Reid,” [Note D,] p. 869n.

[i-i]651, 652 , but an identification of them as one

[j-j]651, 652, 67 unquestionably

[k-k]651aware

[l-l]+72

[m-m]651distance

[* ]It is not pretended that all this was clearly seen by Brown. It is impossible to defend the theory as Brown stated it. He seems to have thought that the essence of extension consisted in divisibility into parts. “A succession of feelings” (he says) “when remembered by the mind which looks back upon them, was found to involve, necessarily, the notion of divisibility into separate parts, and therefore of length, which is only another name for continued divisibility.” (Lecture xxiv, Vol. II, p. 3 of the 19th edition, 1851.) He thought that he had explained all that needed explanation in the idea of space, when he had shown how the notion of continued divisibility got into it. This appears when he says, “It would not be easy for any one to define matter more simply, than as that which has parts, and that which resists our efforts to grasp it; and in our analysis of the feelings of infancy, we have been able to discover how both these notions may have arisen in the mind.” [Ibid., p. 7.] But if divisibility into parts constitutes all our notion of extension, every sensation we have must be identified with extension, for they are all divisible into parts (parts in succession, which Brown thinks sufficient) when they are prolonged beyond the shortest instant of duration which our consciousness recognises. It is probable that Brown did not mean this, but thought that all he had to account for in the conception of space, was its divisibility, because he tacitly assumed that all the rest of the notion was already given in the fact of muscular movement. And this, properly understood, is maintainable; but Brown cannot here be acquitted of a charge to which he is often liable, that of leaving an important philosophical question only half thought out.

[n-n]651, 652 experience

[[*] ]For the term (usually, but mistakenly, attributed to Bacon), see Robert Hooke, Micrographia (London, 1665), p. 54.

[[*] ]Lectures, Vol. II, p. 173.

[* ]Lectures, Vol. II, pp. 174-5. [Hamilton is translating from Ernst Platner, Philosophische Aphorismen, 2 vols. (Leipzig: Schwicktschen Verlag, 1793, 1800), Vol. I, pp. 440-1.]

[o-o]651would

[* ][67] Mr. Mahaffy thinks (pp. xx-xxi) that Platner omitted to ascertain whether his patient was capable of recognising simultaneity; and is of opinion that he could not do so, or that if he could, it must have been owing to his education among people possessed of sight. “The question remains: can we postulate a sense of such simultaneity originally, before any space or extension is given? I am disposed to agree with Brown, that, although we can afterwards analyse them, all simultaneous feelings form originally one mental state; which of course excludes simultaneity until the analysis obtained by the aid of space and extension give us the elements separately. Hence, until at least one body was given as extended, we should not obtain the notion.” Brown may very possibly be right [see Lectures, Vol. I, pp. 294-305], but it does not follow that the analysis necessary to our distinguishing different sensations in one mass of simultaneous feeling, can only take place by means of space and extension. If the simultaneous sensations differ in kind, as a sound, for instance, and a smell, all that is necessary to our being able to distinguish them when together is that we should at some other time have experienced them separate. We should then know the compound, and also the elements: and since these are not chemically fused into a product bearing no resemblance to its factors, but retain when combined their identity with what they are in their separate state, our knowledge of them separately would enable us to recognise them in the compound; in other words, to feel two sensations as simultaneous.

Dr. M‘Cosh says that the experience of other observers (and particularly Mr. Kinghan, Principal of the Institution for the Blind at Belfast) as well as experiments by Dr. M‘Cosh himself on young children born blind, do not confirm Platner’s statement, but prove that those born blind have “a very clear notion of figure and distance, pgot directly from the sense of touch.” ([Examination,] p. 143n.) This is just what might have been expected, for I am far from agreeing with Platner that the notions of figure and distance come originally from sight. The sense of sight is not necessary to give the perception of simultaneity; but, giving a prodigious number of simultaneous sensations in one glance, it greatly quickens all processes dependent on observation of the fact of simultaneousness. A person born blind can acquire, by a more gradual process, all that there is in our notion of Space except the visible picture: but he will be much longer before he realizes it completely, and in the case of Platner’s patient that point does not seem to have been reached.p

[* ]The Senses and the Intellect, pp. 370-4. I now quote from the second edition (1864). The corresponding passage in the first edition begins at p. 363. [Mill’s square brackets.]

[* ]Principles of Psychology [London: Longman, Brown, Green, and Longmans, 1855], p. 224.

[† ]Lectures, Vol. II, p. 172. [See Jean le Rond d’Alembert, Mélanges de littérature, d’histoire, et de philosophie, new ed., 5 vols. (Amsterdam: Chatelain, 1759-67), p. 110.]

[‡ ]Ibid., p. 165.

[* ]Ibid., pp. 167-8. [The words in square brackets are Mill’s.]

[q-q]651 independent

[r-r]+67, 72

[s-s]+72

[[*] ]See George Berkeley, An Essay towards a New Theory of Vision, in Works, 3 vols. (London: Priestley, 1820), Vol. I, pp. 261ff. (§§lii ff.).

[[†] ]Ibid., p. 277 (§lxxix).

[* ]Lectures, Vol. II, p. 160.

[* ][67] The following case, however, which I quote from Dr. M‘Cosh, if correctly reported, would require a considerable modification of the preceding doctrine. “The best reported case” of a person born blind, but who acquired eyesight by means of a surgical operation, “is that of Dr. [Joann Christoph August] Franz of Leipsig ([“Memoir of the Case of a Gentleman born blind,”] Philosophical Transactions of the Royal Society of London, [CXXXI,] 1841 [59-68]). The youth had been born blind, and was seventeen years of age when the experiment was wrought which gave him the use of one eye. When the eye was sufficiently restored to bear the light, a sheet of paper on which two strong black lines had been drawn, the one horizontal, the other vertical, was placed before him at the distance of about three feet. He was now allowed to open the eye, and after attentive examination he called the lines by their right tdenominations,” that is, according to Dr. M‘Cosh, horizontal and vertical.t “ ‘The outline in black of a square, six inches in diameter, within which a circle had been drawn, and within the latter a triangle, was, after careful examination, recognised and correctly described by him.’ ‘At the distance of three feet, and on a level with the eye, a solid cube and a sphere, each of four inches diameter, was placed before him.’ ‘After attentively examining these bodies, he said he saw a quadrangular and a circular figure, and after some consideration he pronounced the one a square and the other a disc. His eye being then closed, the cube was taken away and a disc of equal size substituted and placed next to the sphere. On again opening his eye he observed no difference in these objects, but regarded them both as discs. The solid cube was now placed in a somewhat oblique position before the eye, and close beside it a figure cut out of pasteboard, representing a plane outline prospect of the cube when in this position. Both objects he took to be something like flat quadrates. [qy. quadrilaterals?] A pyramid placed before him with one of its sides towards his eye he saw as a plain [plane?] triangle. This object was now turned a little, so as to present two of its sides to view, but rather more of one side than of the other: after considering and examining it for a long time, he said that this was a very extraordinary figure; it was neither a triangle, nor a quadrangle, nor a circle; he had no idea of it, and could not describe it; in fact, said he, I must give it up. On the conclusion of these experiments, I asked him to describe the sensations the objects had produced, whereupon he said, that immediately on opening his eye he had discovered a difference in the two objects, the cube and the sphere, placed before him, and perceived that they were not drawings; but that he had not been able to form from them the idea of a square and a disc, until he perceived a sensation of what he saw in the points of his fingers, as if he really touched the object. [A very significant fact, both psychologically and physiologically.] When I gave the three bodies (the sphere, cube, and pyramid) into his hand, he was much surprised he had not recognised them as such by sight, as he was well acquainted with mathematical figures by his touch.” ([McCosh, Examination,] pp. 163-5 [quoting Franz, pp. 64-5]. [Mill’s square brackets.])

The case as stated looks like an experimental proof, that not only something which admits of being called extension, but an extension which is promptly identified with that already known by touch, uthough in two dimensions only,u may be perceived by sight at the very first use of the eyes, before the muscular action necessary for directing the eye has been learnt by practice. There is one suspicious circumstance in the recital—the youth’s instantaneous perception that the cube and the sphere were not drawings; for how could one who had never before had any sensation of sight, vdistinguish without help a drawing from its objectv ? Cheselden’s patient was for a long time deceived by pictures, and asked which was the lying sense, feeling or seeing. [See William Cheselden, “An Account of some Observations,” Philosophical Transactions of the Royal Society of London, XXXV (1728), 449.] We ought, moreover, to have been expressly told whether, previous to the operation, the blindness was absolutely complete; which in many of the cases cited by Mr. Samuel Bailey it was not, and, according to Cheselden, in cases of congenital cataract it seldom is so. [Ibid.,p. 447.] If no material circumstance is omitted in the report of Dr. Franz’s case, the doctrine in the text will require a certain amount of correction. What is there called a rudimentary conception of figure by the eye, must be more than rudimentary; it must be, in its way, considerably developed; and it must be such that “after attentive examination” it could be recognised as corresponding with the circles and quadrangles already known by touch. On this last point the report does not agree with other recorded cases. In a recent case, for example, recorded by Mr. Nunneley (I quote at second hand from Professor Fraser in the North British Review) the boy could indeed, after couching, “at once perceive a difference in the shapes of objects,” could see that the cube and the sphere “were not of the same visible figure,” but could not tell which was which: “it was not till they had been many times placed in his hands, that he learnt to distinguish by sight the one which he had just had in his hands from the other placed beside it. He gradually became more correct in his judgments, but it was only after several days that he could tell by the eye alone which was the sphere and which the cube; when asked, he always, before answering, wished to take both in his hands. Even when this was allowed, when immediately afterwards the objects were placed before the eyes, he was not certain of the figure.” [A. C. Fraser, “Berkeley’s Theory of Vision,” North British Review, XLI (Aug., 1864), 215, who is quoting Thomas Nunneley, On the Organs of Vision (London: Churchill, 1838), p. 32.]

If Dr. Franz’s case is fairly reported, his patient was probably of more than ordinary natural quickness of observation, and identified the figures not by resemblance proper, but by analogy, or resemblance of relations. Though beholding for the first time a visual square and circle, he was no doubt aware through the persons who surrounded him, that the objects shown to his sight were objects which could be touched—which he already knew by touch. During the “careful examination” and “consideration” which preceded his recognition of them, he was probably employed in asking himself to what, in his experience of tangible objects, these visible objects bore the greatest affinity. Now, he was “well acquainted with mathematical figures by touch,” and had therefore acquired a complete idea of a closed figure, and of the boundary which incloses it—the outline separating object from not-object. A relation similar to that between a tangible figure and its boundary, exists between the visual periphery and the mass of colour it incloses. This mere analogy might be sufficient to direct his choice, when a visual object had at any rate to be identified with a tangible. The grand difficulty was in discovering that any visual object was the same with any tangible: but, this difficulty once surmounted by the information of others, a small circumstance might give him a hint for pairing the one class of objects with the other. In his familiarity, by touch and the muscles, with (let us say) a triangular outline, he had become aware of sudden and sharp bends in it, and knew that there were three of these in the tangible periphery. There was the same number of peculiar points in the visual outline, which might not spontaneously have reminded him of the bends he knew by touch, but, if a choice had to be made, were more analogous to them than anything in a circular outline. Being required therefore to give to this object the name of something tangible, he was naturally led to calling it a triangle. It is by no means evident that if left entirely to himself, he would have found out, except by gradual experience, that the phænomenon analogous to extension, which he perceived by sight, was the extension which he already knew by touch. I may add, that since we have from sight distinctive sensations answering to the various figures, it is no more than natural that these sensations, however unlike the tactual sensations which they represent, should have relations among themselves, resembling the mutual relations of those. wThe same explanation may probably serve for the lad’s ability to distinguish by sight a vertical line from a horizontal. He was probably told that one of them was horizontal and the other vertical, and was only asked which was which; and without further information we cannot tell what small circumstance may have determined him to guess the one rather than the other.w To sum up my view of Dr. Franz’s case, it does not prove that we perceive extension by sight, but only that we have discriminative sensations of sight, corresponding to all the diversities of superficial extension: but, if rightly reported, it greatly widens the range of those discriminative sensations, and almost shows that by sight alone we might rise to the height of Reid’s Geometry of Visibles [see Reid’s Inquiry, pp. 147-52].

[* ]The Senses and the Intellect, 2nd ed., pp. 376-7; 1st ed., p. 369. To this passage, Mr. Bain has appended, in his second edition the following instructive note:

“In following a wide ranging movement, or in expatiating over a large prospect, we must move the eyes or the head; and probably every one would allow that, in such a case, feelings of movement make a part of our sensation and our subsequent idea. The notion of a mountain evidently contains feelings of visual movement. But when we look at a circle, say, one tenth of an inch in diameter, the eye can take in the whole of it without movement, and we might suppose that the sensation is, in that case, purely optical, there being no apparent necessity for introducing the muscular consciousness. A characteristic optical impression is produced; we should be able to discriminate between the small circle and a square, or an oval, or between it and a somewhat larger or somewhat smaller circle, from the mere optical difference of the effect on the retina. Why then may we not say, that, through the luminous tracing alone, we have the feeling of visible form?

By making an extreme supposition of this nature, it is possible to remove the case from a direct experimental test. We may still, however, see very strong grounds for maintaining the presence of a muscular element even in this instance. In the first place, our notions of form are manifestly obtained by working on the large scale, or by the survey of objects of such magnitude as to demand the sweep of the eye, in order to comprehend them. We lay the foundations of our knowledge of visible outline in circumstances where the eye must be active, and must mix its own activity with the retinal feelings. The idea of a circle is first gained by moving the eye round some circular object of considerable size. Having done this, we transfer the fact of motion to smaller circles, although they would not of themselves demand an extensive ocular sweep. So that when we look at a little round body, we are already pre-occupied with the double nature of visible form, and are not in a position to say how we should regard it, if that were our first experience of a circle.

But, in the second place, the essential import of visible form is something not attainable without the experience of moving the eye. If we looked at a little round spot, we should know an optical difference between it and a triangular spot, and we should recognise it as identical with another round spot; but that is merely retinal knowledge, or optical discrimination. That would not be to recognise form, because by form we never mean so little as a mere change of colour. We mean by a round form something that would take a given sweep of the eye to comprehend it; and unless we identify the small spot with the circles previously seen, we do not perceive it to be a circle. It may remain in our mind as a purely optical meaning; but we can never cross the chasm that separates an optical meaning from an effect combining light and movement, in any other way than by bringing in an experience of movement.” (Pp. 377n-8n.)

[* ]“Dissertations on Reid,” [Note D,] p. 861n.

[x-x]651 the

[[*] ]See Bain, The Senses and the Intellect, 1st ed., p. 178; see also McCosh, Examination, p. 153, where Bain’s view is discussed.

[y-y]651volume

[[*] ]See pp. 223-4 above.

[[†] ]Cheselden, p. 450.

[* ]I may here observe that Sir W. Hamilton (and the same mistake has been made by Mr. Bailey [A Review of Berkeley’s Theory of Vision, pp. 166-83]) considers Cheselden’s case as evidence that the “perception of externality,” as distinguished from that of distance from the eye, is given by sight as well as by touch, because the young man said that objects at first seemed “to touch his eyes, as what he felt did his skin.” [Cheselden, p. 448.] He seems to think that, on the other theory, the boy should have been metaphysician enough to recognise in the perception “a mere affection of the organ,” or at least should have perceived the objects “as if in his eyes.” (Foot-note to Reid, p. 177n.) But he was not accustomed to conceive tangible objects as if in his fingers. He conceived them as touching his fingers: and he simply transferred the experience of touch to the newly-acquired sense. All his notions of perception were associated with direct contact; and as he did not perceive any of the objects of sight to be at a distance from the organ by which he perceived them, he concluded that they must be in contact with it.

zMr. Nunneley’s case, on this point, agrees with Cheselden’s. The boy “said everything touched his eyes, and walked carefully about with his hands held up before him, to prevent things hurting his eyes by touching them.”z

[[*] ]See Marie François Pierre Gonthier Maine de Biran, Nouvelles Considérations sur les rapports du physique et du moral de l’homme, ed. Victor Cousin (Paris: Ladrange, 1834), pp. 96-7.

[[†] ]Rey Régis was a pseudonym for Cazillac; the reference is to his Histoire naturelle et raisonnée de l’âme, 2 vols. (London [Lyons], 1789), Vol. I, p. 27.

[* ]“Dissertations on Reid,” [Note D,] p. 875n.

[[‡] ]See pp. 222-3 above.

[a]651, 652 fully

[† ][67] Dr. M‘Cosh says: “This case is valueless, as evidently the functions of the nervous apparatus were deranged.” ([Examination,] p. 151n.) I am far from pretending that this single experiment is conclusive; but I can as little admit that it ought to count for nothing. The functions of the motor nerves were deranged; but no derangement appears to have been remarked in those of the nerves of sensation; unless, by a petitio principii, the incapacity of localizing the sensations is considered to prove it. We cannot indeed prove that those nerves were not also in a morbid state: but pathological cases, which are admitted to be the nearest equivalents in physiology to experiments in inorganic science, would lose all their scientific value if it could be assumed without evidence that the disease extended to other functions than those in which it was observed. Even if a physical derangement were proved, one not unimportant point would have been ascertained by the experiment—that a morbid affection may take away the power of localizing sensations, without taking away the sensations. Localization, therefore, does not depend on the same conditions with the sensations themselves, still less is it inseparably involved in them.

[* ]“Dissertations on Reid,” [Note D*,] pp. 881-2.

[* ]Ibid., [Note D,] p. 842.

[b-b]651 these

[† ]The Senses and the Intellect [London: Parker, 1855], pp. 113-17. My first extract is from the original edition; for in the one recently published (and enriched by many valuable improvements) the exposition I now quote is given more summarily, and in a manner otherwise less suited for my purpose. [2nd ed. (London: Longman, Green, Longman, Roberts, and Green, 1864), pp. 111-15.]

gDr. M‘Cosh, without any warrant, speaks of Mr. Bain as having “elaborated into a minute system the general statements scattered throughout Mr. Mill’s Logic” ([Examination,] p. 121); and in another passage refers to him and to Mr. Herbert Spencer (Mr. Herbert Spencer!) as merely following out an investigation indicated by me. (Ibid., pp. 123-4.) Coleridge reminded one of his critics, that there are such things in the world as springs, and that the water a man draws does not necessarily come from a hole made in another man’s cistern. [“Preface to Christabel,” in Christabel; Kubla Khan, a Vision; The Pains of Sleep (London: Murray, 1816), p. vi.] Mr. Bain did not stand in need of any predecessor except our common precursors, and has taught much more to me, on these subjects, than there is any reasonable probability that I can have taught to him. Dr. M‘Cosh falls into a corresponding mistake concerning myself, when he ascribes my regarding it “as impossible for the mind to rise to first or final causes, or to know the nature of things,” to “the influence” of M. Comte. (Examination, pp. 7-8.) The larger half of my System of Logic, including all its fundamental doctrines, was written before I had even seen the Cours de Philosophie Positive. That work was indebted to M. Comte for many valuable thoughts, but a short list would exhaust the chapters, and even the pages, which contain them. [See the Textual Introduction to System of Logic, Collected Works, Vol. VII, pp. lxxviii, lxxxii-lxxxiii, and xc-xci.] As for the general doctrine which Dr. M‘Cosh’s words so imperfectly express—that our knowledge is only of the coexistences and sequences, or the similitudes, of phænomena; I was familiar with it before I was out of boyhood from the teachings of my father, who had learnt it where M. Comte learnt it—from the methods of physical science, and the writings of their philosophical predecessors. Ever since the days of Hume, that doctrine has been the general property of the philosophic world. From the time of Brown it has entered even into popular philosophy.ghI have given a brief history of it in Auguste Comte and Positivism.h [See Collected Works, Vol. X, pp. 265-9.]

[* ][67] Mr. Mahaffy thinks (pp. xx-xxi) that Platner omitted to ascertain whether his patient was capable of recognising simultaneity; and is of opinion that he could not do so, or that if he could, it must have been owing to his education among people possessed of sight. “The question remains: can we postulate a sense of such simultaneity originally, before any space or extension is given? I am disposed to agree with Brown, that, although we can afterwards analyse them, all simultaneous feelings form originally one mental state; which of course excludes simultaneity until the analysis obtained by the aid of space and extension give us the elements separately. Hence, until at least one body was given as extended, we should not obtain the notion.” Brown may very possibly be right [see Lectures, Vol. I, pp. 294-305], but it does not follow that the analysis necessary to our distinguishing different sensations in one mass of simultaneous feeling, can only take place by means of space and extension. If the simultaneous sensations differ in kind, as a sound, for instance, and a smell, all that is necessary to our being able to distinguish them when together is that we should at some other time have experienced them separate. We should then know the compound, and also the elements: and since these are not chemically fused into a product bearing no resemblance to its factors, but retain when combined their identity with what they are in their separate state, our knowledge of them separately would enable us to recognise them in the compound; in other words, to feel two sensations as simultaneous.

Dr. M‘Cosh says that the experience of other observers (and particularly Mr. Kinghan, Principal of the Institution for the Blind at Belfast) as well as experiments by Dr. M‘Cosh himself on young children born blind, do not confirm Platner’s statement, but prove that those born blind have “a very clear notion of figure and distance, pgot directly from the sense of touch.” ([Examination,] p. 143n.) This is just what might have been expected, for I am far from agreeing with Platner that the notions of figure and distance come originally from sight. The sense of sight is not necessary to give the perception of simultaneity; but, giving a prodigious number of simultaneous sensations in one glance, it greatly quickens all processes dependent on observation of the fact of simultaneousness. A person born blind can acquire, by a more gradual process, all that there is in our notion of Space except the visible picture: but he will be much longer before he realizes it completely, and in the case of Platner’s patient that point does not seem to have been reached.p

[* ][67] The following case, however, which I quote from Dr. M‘Cosh, if correctly reported, would require a considerable modification of the preceding doctrine. “The best reported case” of a person born blind, but who acquired eyesight by means of a surgical operation, “is that of Dr. [Joann Christoph August] Franz of Leipsig ([“Memoir of the Case of a Gentleman born blind,”] Philosophical Transactions of the Royal Society of London, [CXXXI,] 1841 [59-68]). The youth had been born blind, and was seventeen years of age when the experiment was wrought which gave him the use of one eye. When the eye was sufficiently restored to bear the light, a sheet of paper on which two strong black lines had been drawn, the one horizontal, the other vertical, was placed before him at the distance of about three feet. He was now allowed to open the eye, and after attentive examination he called the lines by their right tdenominations,” that is, according to Dr. M‘Cosh, horizontal and vertical.t “ ‘The outline in black of a square, six inches in diameter, within which a circle had been drawn, and within the latter a triangle, was, after careful examination, recognised and correctly described by him.’ ‘At the distance of three feet, and on a level with the eye, a solid cube and a sphere, each of four inches diameter, was placed before him.’ ‘After attentively examining these bodies, he said he saw a quadrangular and a circular figure, and after some consideration he pronounced the one a square and the other a disc. His eye being then closed, the cube was taken away and a disc of equal size substituted and placed next to the sphere. On again opening his eye he observed no difference in these objects, but regarded them both as discs. The solid cube was now placed in a somewhat oblique position before the eye, and close beside it a figure cut out of pasteboard, representing a plane outline prospect of the cube when in this position. Both objects he took to be something like flat quadrates. [qy. quadrilaterals?] A pyramid placed before him with one of its sides towards his eye he saw as a plain [plane?] triangle. This object was now turned a little, so as to present two of its sides to view, but rather more of one side than of the other: after considering and examining it for a long time, he said that this was a very extraordinary figure; it was neither a triangle, nor a quadrangle, nor a circle; he had no idea of it, and could not describe it; in fact, said he, I must give it up. On the conclusion of these experiments, I asked him to describe the sensations the objects had produced, whereupon he said, that immediately on opening his eye he had discovered a difference in the two objects, the cube and the sphere, placed before him, and perceived that they were not drawings; but that he had not been able to form from them the idea of a square and a disc, until he perceived a sensation of what he saw in the points of his fingers, as if he really touched the object. [A very significant fact, both psychologically and physiologically.] When I gave the three bodies (the sphere, cube, and pyramid) into his hand, he was much surprised he had not recognised them as such by sight, as he was well acquainted with mathematical figures by his touch.” ([McCosh, Examination,] pp. 163-5 [quoting Franz, pp. 64-5]. [Mill’s square brackets.])

The case as stated looks like an experimental proof, that not only something which admits of being called extension, but an extension which is promptly identified with that already known by touch, uthough in two dimensions only,u may be perceived by sight at the very first use of the eyes, before the muscular action necessary for directing the eye has been learnt by practice. There is one suspicious circumstance in the recital—the youth’s instantaneous perception that the cube and the sphere were not drawings; for how could one who had never before had any sensation of sight, vdistinguish without help a drawing from its objectv ? Cheselden’s patient was for a long time deceived by pictures, and asked which was the lying sense, feeling or seeing. [See William Cheselden, “An Account of some Observations,” Philosophical Transactions of the Royal Society of London, XXXV (1728), 449.] We ought, moreover, to have been expressly told whether, previous to the operation, the blindness was absolutely complete; which in many of the cases cited by Mr. Samuel Bailey it was not, and, according to Cheselden, in cases of congenital cataract it seldom is so. [Ibid.,p. 447.] If no material circumstance is omitted in the report of Dr. Franz’s case, the doctrine in the text will require a certain amount of correction. What is there called a rudimentary conception of figure by the eye, must be more than rudimentary; it must be, in its way, considerably developed; and it must be such that “after attentive examination” it could be recognised as corresponding with the circles and quadrangles already known by touch. On this last point the report does not agree with other recorded cases. In a recent case, for example, recorded by Mr. Nunneley (I quote at second hand from Professor Fraser in the North British Review) the boy could indeed, after couching, “at once perceive a difference in the shapes of objects,” could see that the cube and the sphere “were not of the same visible figure,” but could not tell which was which: “it was not till they had been many times placed in his hands, that he learnt to distinguish by sight the one which he had just had in his hands from the other placed beside it. He gradually became more correct in his judgments, but it was only after several days that he could tell by the eye alone which was the sphere and which the cube; when asked, he always, before answering, wished to take both in his hands. Even when this was allowed, when immediately afterwards the objects were placed before the eyes, he was not certain of the figure.” [A. C. Fraser, “Berkeley’s Theory of Vision,” North British Review, XLI (Aug., 1864), 215, who is quoting Thomas Nunneley, On the Organs of Vision (London: Churchill, 1838), p. 32.]

If Dr. Franz’s case is fairly reported, his patient was probably of more than ordinary natural quickness of observation, and identified the figures not by resemblance proper, but by analogy, or resemblance of relations. Though beholding for the first time a visual square and circle, he was no doubt aware through the persons who surrounded him, that the objects shown to his sight were objects which could be touched—which he already knew by touch. During the “careful examination” and “consideration” which preceded his recognition of them, he was probably employed in asking himself to what, in his experience of tangible objects, these visible objects bore the greatest affinity. Now, he was “well acquainted with mathematical figures by touch,” and had therefore acquired a complete idea of a closed figure, and of the boundary which incloses it—the outline separating object from not-object. A relation similar to that between a tangible figure and its boundary, exists between the visual periphery and the mass of colour it incloses. This mere analogy might be sufficient to direct his choice, when a visual object had at any rate to be identified with a tangible. The grand difficulty was in discovering that any visual object was the same with any tangible: but, this difficulty once surmounted by the information of others, a small circumstance might give him a hint for pairing the one class of objects with the other. In his familiarity, by touch and the muscles, with (let us say) a triangular outline, he had become aware of sudden and sharp bends in it, and knew that there were three of these in the tangible periphery. There was the same number of peculiar points in the visual outline, which might not spontaneously have reminded him of the bends he knew by touch, but, if a choice had to be made, were more analogous to them than anything in a circular outline. Being required therefore to give to this object the name of something tangible, he was naturally led to calling it a triangle. It is by no means evident that if left entirely to himself, he would have found out, except by gradual experience, that the phænomenon analogous to extension, which he perceived by sight, was the extension which he already knew by touch. I may add, that since we have from sight distinctive sensations answering to the various figures, it is no more than natural that these sensations, however unlike the tactual sensations which they represent, should have relations among themselves, resembling the mutual relations of those. wThe same explanation may probably serve for the lad’s ability to distinguish by sight a vertical line from a horizontal. He was probably told that one of them was horizontal and the other vertical, and was only asked which was which; and without further information we cannot tell what small circumstance may have determined him to guess the one rather than the other.w To sum up my view of Dr. Franz’s case, it does not prove that we perceive extension by sight, but only that we have discriminative sensations of sight, corresponding to all the diversities of superficial extension: but, if rightly reported, it greatly widens the range of those discriminative sensations, and almost shows that by sight alone we might rise to the height of Reid’s Geometry of Visibles [see Reid’s Inquiry, pp. 147-52].

[* ]I may here observe that Sir W. Hamilton (and the same mistake has been made by Mr. Bailey [A Review of Berkeley’s Theory of Vision, pp. 166-83]) considers Cheselden’s case as evidence that the “perception of externality,” as distinguished from that of distance from the eye, is given by sight as well as by touch, because the young man said that objects at first seemed “to touch his eyes, as what he felt did his skin.” [Cheselden, p. 448.] He seems to think that, on the other theory, the boy should have been metaphysician enough to recognise in the perception “a mere affection of the organ,” or at least should have perceived the objects “as if in his eyes.” (Foot-note to Reid, p. 177n.) But he was not accustomed to conceive tangible objects as if in his fingers. He conceived them as touching his fingers: and he simply transferred the experience of touch to the newly-acquired sense. All his notions of perception were associated with direct contact; and as he did not perceive any of the objects of sight to be at a distance from the organ by which he perceived them, he concluded that they must be in contact with it.

zMr. Nunneley’s case, on this point, agrees with Cheselden’s. The boy “said everything touched his eyes, and walked carefully about with his hands held up before him, to prevent things hurting his eyes by touching them.”z

[gDr. M‘Cosh, without any warrant, speaks of Mr. Bain as having “elaborated into a minute system the general statements scattered throughout Mr. Mill’s Logic” ([Examination,] p. 121); and in another passage refers to him and to Mr. Herbert Spencer (Mr. Herbert Spencer!) as merely following out an investigation indicated by me. (Ibid., pp. 123-4.) Coleridge reminded one of his critics, that there are such things in the world as springs, and that the water a man draws does not necessarily come from a hole made in another man’s cistern. [“Preface to Christabel,” in Christabel; Kubla Khan, a Vision; The Pains of Sleep (London: Murray, 1816), p. vi.] Mr. Bain did not stand in need of any predecessor except our common precursors, and has taught much more to me, on these subjects, than there is any reasonable probability that I can have taught to him. Dr. M‘Cosh falls into a corresponding mistake concerning myself, when he ascribes my regarding it “as impossible for the mind to rise to first or final causes, or to know the nature of things,” to “the influence” of M. Comte. (Examination, pp. 7-8.) The larger half of my System of Logic, including all its fundamental doctrines, was written before I had even seen the Cours de Philosophie Positive. That work was indebted to M. Comte for many valuable thoughts, but a short list would exhaust the chapters, and even the pages, which contain them. [See the Textual Introduction to System of Logic, Collected Works, Vol. VII, pp. lxxviii, lxxxii-lxxxiii, and xc-xci.] As for the general doctrine which Dr. M‘Cosh’s words so imperfectly express—that our knowledge is only of the coexistences and sequences, or the similitudes, of phænomena; I was familiar with it before I was out of boyhood from the teachings of my father, who had learnt it where M. Comte learnt it—from the methods of physical science, and the writings of their philosophical predecessors. Ever since the days of Hume, that doctrine has been the general property of the philosophic world. From the time of Brown it has entered even into popular philosophy.g]+67, 72

[hI have given a brief history of it in Auguste Comte and Positivism.h]+72

[pgot directly from the sense of touch.” ([Examination,] p. 143n.) This is just what might have been expected, for I am far from agreeing with Platner that the notions of figure and distance come originally from sight. The sense of sight is not necessary to give the perception of simultaneity; but, giving a prodigious number of simultaneous sensations in one glance, it greatly quickens all processes dependent on observation of the fact of simultaneousness. A person born blind can acquire, by a more gradual process, all that there is in our notion of Space except the visible picture: but he will be much longer before he realizes it completely, and in the case of Platner’s patient that point does not seem to have been reached.p][manuscript fragment exists; see Appendix A below]

[tdenominations,” that is, according to Dr. M‘Cosh, horizontal and vertical.t]67 denominations”—what?

[uthough in two dimensions only,u]+72

[vdistinguish without help a drawing from its objectv]67 know what a drawing is

[wThe same explanation may probably serve for the lad’s ability to distinguish by sight a vertical line from a horizontal. He was probably told that one of them was horizontal and the other vertical, and was only asked which was which; and without further information we cannot tell what small circumstance may have determined him to guess the one rather than the other.w]+72

[zMr. Nunneley’s case, on this point, agrees with Cheselden’s. The boy “said everything touched his eyes, and walked carefully about with his hands held up before him, to prevent things hurting his eyes by touching them.”z]+67, 72