The Online Library of Liberty

A project of Liberty Fund, Inc.

• Key to Abbreviations and References
• General Introduction
• Introduction
• The History of Astronomy
• The History of the Ancient Physics and the History of the Ancient Logics and Metaphysics
• The History of Astronomy
• Section I: Of the Effect of Unexpectedness, Or of Surprise
• Section II: Of Wonder, Or of the Effects of Novelty
• Section III: Of the Origin of Philosophy
• Section IV: The History of Astronomy
• Of the External Senses
• Of the Nature of That Imitation Which Takes Place In What Are Called the Imitative Arts/of the Affinity Between Music, Dancing, and Poetry
• Of the Affinity Between Music, Dancing, and Poetry
• Of the Affinity Between Certain English and Italian Verses
• Contributions to the Edinburgh Review of 1755–56 Review of Johnson’s Dictionary a Letter to the Authors of the Edinburgh Review
• Review of Johnson’s Dictionary
• A Letter to the Authors of the Edinburgh Review.
• Appendix: Passages Quoted From Rousseau
• Preface and Dedication to William Hamilton’s Poems On Several Occasions
• Account of the Life and Writings of Adam Smith, Ll.d. From the Transactions of the Royal Society of Edinburgh [read By Mr Stewart, January 21, and March 18, 1793]

the HISTORY of ASTRONOMY

Wonder, Surprise, and Admiration, are words which, though often confounded, denote, in our language, sentiments that are indeed allied, but that are in some respects different also, and distinct from one another. What is new and singular, excites that sentiment which, in strict propriety, is called Wonder; what is unexpected, Surprise; and what is great or beautiful, Admiration.

We wonder at all extraordinary and uncommon objects, at all the rarer phaenomena of nature, at meteors, comets, eclipses, at singular plants and animals, and at every thing, in short, with which we have before been either little or not at all acquainted; and we still wonder, though forewarned of what we are to see.

We are surprised at those things which we have seen often, but which we least of all expected to meet with in the place where we find them; we are surprised at the sudden appearance of a friend, whom we have seen a thousand times, but whom we did not imagine we were to see then.

We admire the beauty of a plain or the greatness of a mountain, though we have seen both often before, and though nothing appears to us in either, but what we had expected with certainty to see.

Whether this criticism upon the precise meaning of these words be just, is of little importance. I imagine it is just, though I acknowledge, that the best writers in our language have not always made use of them according to it. Milton, upon the appearance of Death to Satan, says, that

• The Fiend what this might be admir’d;
• Admir’d, not fear’d.1 —

But if this criticism be just, the proper expression should have been wonder’d.—Dryden, upon the discovery of Iphigenia sleeping, says, that

• The fool of nature stood with stupid eyes
• And gaping mouth, that testified surprise.2

But what Cimon must have felt upon this occasion could not so much be Surprise, as Wonder and Admiration. All that I contend for is, that the sentiments excited by what is new, by what is unexpected, and by what is great and beautiful, are really different, however the words made use of to express them may sometimes be confounded. Even the admiration which is excited by beauty, is quite different (as will appear more fully hereafter) from that which is inspired by greatness, though we have but one word to denote them.

These sentiments, like all others when inspired by one and the same object, mutually support and enliven one another: an object with which we are quite familiar, and which we see every day, produces, though both great and beautiful, but a small effect upon us; because our admiration is not supported either by Wonder or by Surprise: and if we have heard a very accurate description of a monster, our Wonder will be the less when we see it; because our previous knowledge of it will in a great measure prevent our Surprise.

It is the design of this Essay to consider particularly the nature and causes of each of these sentiments, whose influence is of far wider extent than we should be apt upon a careless view to imagine. I shall begin with Surprise.

SECTION I

Of the Effect of Unexpectedness, or of Surprise

When an object of any kind, which has been for some time expected and foreseen, presents itself, whatever be the emotion which it is by nature fitted to excite, the mind must have been prepared for it, and must even in some measure have conceived it before–hand; because the idea of the object having been so long present to it, must have before–hand excited some degree of the same emotion which the object itself would excite: the change, therefore, which its presence produces comes thus to be less considerable, and the emotion or passion which it excites glides gradually and easily into the heart, without violence, pain, or difficulty.1

But the contrary of all this happens when the object is unexpected; the passion is then poured in all at once upon the heart, which is thrown, if it is a strong passion, into the most violent and convulsive emotions, such as sometimes cause immediate death; sometimes, by the suddenness of the extacy, so entirely disjoint the whole frame of the imagination, that it never after returns to its former tone and composure, but falls either into a frenzy or habitual lunacy; and such as almost always occasion a momentary loss of reason, or of that attention to other things which our situation or our duty requires.

How much we dread the effects of the more violent passions, when they come suddenly upon the mind, appears from those preparations which all men think necessary when going to inform any one of what is capable of exciting them. Who would choose all at once to inform his friend of an extraordinary calamity that had befallen him, without taking care before–hand, by alarming him with an uncertain fear, to announce, if one may say so, his misfortune, and thereby prepare and dispose him for receiving the tidings?

Those panic terrors which sometimes seize armies in the field, or great cities, when an enemy is in the neighbourhood, and which deprive for a time the most determined of all deliberate judgments, are never excited but by the sudden apprehension of unexpected danger. Such violent consternations, which at once confound whole multitudes, benumb their understandings, and agitate their hearts, with all the agony of extravagant fear, can never be produced by any foreseen danger, how great soever. Fear, though naturally a very strong passion, never rises to such excesses, unless exasperated both by Wonder, from the uncertain nature of the danger, and by Surprise, from the suddenness of the apprehension.

Surprise, therefore, is not to be regarded as an original emotion of a species distinct from all others. The violent and sudden change produced upon the mind, when an emotion of any kind is brought suddenly upon it, constitutes the whole nature of Surprise.

But when not only a passion and a great passion comes all at once upon the mind, but when it comes upon it while the mind is in the mood most unfit for conceiving it, the Surprise is then the greatest. Surprises of joy when the mind is sunk into grief, or of grief when it is elated with joy, are therefore the most unsupportable. The change is in this case the greatest possible. Not only a strong passion is conceived all at once, but a strong passion the direct opposite of that which was before in possession of the soul. When a load of sorrow comes down upon the heart that is expanded and elated with gaiety and joy, it seems not only to damp and oppress it, but almost to crush and bruise it, as a real weight would crush and bruise the body. On the contrary, when from an unexpected change of fortune, a tide of gladness seems, if I may say so, to spring up all at once within it, when depressed and contracted with grief and sorrow, it feels as if suddenly extended and heaved up with violent and irresistible force, and is torn with pangs of all others most exquisite, and which almost always occasion faintings, deliriums, and sometimes instant death. For it may be worth while to observe, that though grief be a more violent passion than joy, as indeed all uneasy sensations seem naturally more pungent than the opposite agreeable ones, yet of the two, Surprises of joy are still more insupportable than Surprises of grief. We are told2 that after the battle of Thrasimenus, while a Roman lady, who had been informed that her son was slain in the action, was sitting alone bemoaning her misfortunes, the young man who escaped came suddenly into the room to her, and that she cried out and expired instantly in a transport of joy. Let us suppose the contrary of this to have happened, and that in the midst of domestic festivity and mirth, he had suddenly fallen down dead at her feet, is it likely that the effects would have been equally violent? I imagine not. The heart springs to joy with a sort of natural elasticity, it abandons itself to so agreeable an emotion, as soon as the object is presented; it seems to pant and leap forward to meet it, and the passion in its full force takes at once entire and complete possession of the soul. But it is otherways with grief; the heart recoils from, and resists the first approaches of that disagreeable passion, and it requires some time before the melancholy object can produce its full effect. Grief comes on slowly and gradually, nor ever rises at once to that height of agony to which it is increased after a little time. But joy comes rushing upon us all at once like a torrent. The change produced therefore by a Surprise of joy is more sudden, and upon that account more violent and apt to have more fatal effects, than that which is occasioned by a Surprise of grief; there seems too to be something in the nature of Surprise, which makes it unite more easily with the brisk and quick motion of joy, than with the slower and heavier movement of grief. Most men who can take the trouble to recollect, will find that they have heard of more people who died or became distracted with sudden joy, than with sudden grief. Yet from the nature of human affairs, the latter must be much more frequent than the former. A man may break his leg, or lose his son, though he has had no warning of either of these events, but he can hardly meet with an extraordinary piece of good fortune, without having had some foresight of what was to happen.

Not only grief and joy but all the other passions, are more violent, when opposite extremes succeed each other. Is any resentment so keen as what follows the quarrels of lovers, or any love so passionate as what attends their reconcilement?

Even the objects of the external senses affect us in a more lively manner, when opposite extremes succeed to, or are placed beside each other. Moderate warmth seems intolerable heat if felt after extreme cold. What is bitter will seem more so when tasted after what is very sweet; a dirty white will seem bright and pure when placed by a jet black. The vivacity in short of every sensation, as well as of every sentiment, seems to be greater or less in proportion to the change made by the impression of either upon the situation of the mind or organ; but this change must necessarily be the greatest when opposite sentiments and sensations are contrasted, or succeed immediately to one another. Both sentiments and sensations are then the liveliest; and this superior vivacity proceeds from nothing but their being brought upon the mind or organ when in a state most unfit for conceiving them.

As the opposition of contrasted sentiments heightens their vivacity, so the resemblance of those which immediately succeed each other renders them more faint and languid. A parent who has lost several children immediately after one another, will be less affected with the death of the last than with that of the first, though the loss in itself be, in this case, undoubtedly greater; but his mind being already sunk into sorrow, the new misfortune seems to produce no other effect than a continuance of the same melancholy, and is by no means apt to occasion such transports of grief as are ordinarily excited by the first calamity of the kind; he receives it, though with great dejection, yet with some degree of calmness and composure, and without any thing of that anguish and agitation of mind which the novelty of the misfortune is apt to occasion. Those who have been unfortunate through the whole course of their lives are often indeed habitually melancholy, and sometimes peevish and splenetic, yet upon any fresh disappointment, though they are vexed and complain a little, they seldom fly out into any more violent passion, and never fall into those transports of rage or grief which often, upon the like occasions, distract the fortunate and successful.

Upon this are founded, in a great measure, some of the effects of habit and custom. It is well known that custom deadens the vivacity of both pain and pleasure, abates the grief we should feel for the one, and weakens the joy we should derive from the other. The pain is supported without agony, and the pleasure enjoyed without rapture: because custom and the frequent repetition of any object comes at last to form and bend the mind or organ to that habitual mood and disposition which fits them to receive its impression, without undergoing any very violent change.

SECTION II

Of Wonder, or of the Effects of Novelty

It is evident that the mind takes pleasure in observing the resemblances that are discoverable betwixt different objects. It is by means of such observations that it endeavours to arrange and methodise all its ideas, and to reduce them into proper classes and assortments. Where it can observe but one single quality, that is common to a great variety of otherwise widely different objects, that single circumstance will be sufficient for it to connect them all together, to reduce them to one common class, and to call them by one general name. It is thus that all things endowed with a power of self–motion, beasts, birds, fishes, insects, are classed under the general name of Animal; and that these again, along with those which want that power, are arranged under the still more general word Substance: and this is the origin of those assortments of objects and ideas which in the schools are called Genera and Species, and of those abstract and general names, which in all languages are made use of to express them.1

The further we advance in knowledge and experience, the greater number of divisions and subdivisions of those Genera and Species we are both inclined and obliged to make. We observe a greater variety of particularities amongst those things which have a gross resemblance; and having made new divisions of them, according to those newly–observed particularities, we are then no longer to be satisfied with being able to refer an object to a remote genus, or very general class of things, to many of which it has but a loose and imperfect resemblance. A person, indeed, unacquainted with botany may expect to satisfy your curiosity, by telling you, that such a vegetable is a weed, or, perhaps in still more general terms, that it is a plant. But a botanist will neither give nor accept of such an answer. He has broke and divided that great class of objects into a number of inferior assortments, according to those varieties which his experience has discovered among them; and he wants to refer each individual plant to some tribe of vegetables, with all of which it may have a more exact resemblance, than with many things comprehended under the extensive genus of plants. A child imagines that it gives a satisfactory answer when it tells you, that an object whose name it knows not is a thing, and fancies that it informs you of something, when it thus ascertains to which of the two most obvious and comprehensive classes of objects a particular impression ought to be referred; to the class of realities or solid substances which is calls things, or to that of appearances which it calls nothings.

Whatever, in short, occurs to us we are fond of referring to some species or class of things, with all of which it has a nearly exact resemblance; and though we often know no more about them than about it, yet we are apt to fancy that by being able to do so, we show ourselves to be better acquainted with it, and to have a more thorough insight into its nature. But when something quite new and singular is presented, we feel ourselves incapable of doing this. The memory cannot, from all its stores, cast up any image that nearly resembles this strange appearance. If by some of its qualities it seems to resemble, and to be connected with a species which we have before been acquainted with, it is by others separated and detached from that, and from all the other assortments of things we have hitherto been able to make. It stands alone and by itself in the imagination, and refuses to be grouped or confounded with any set of objects whatever. The imagination and memory exert themselves to no purpose, and in vain look around all their classes of ideas in order to find one under which it may be arranged. They fluctuate to no purpose from thought to thought, and we remain still uncertain and undetermined where to place it, or what to think of it. It is this fluctuation and vain recollection, together with the emotion or movement of the spirits2 that they excite, which constitute the sentiment properly called Wonder, and which occasion that staring, and sometimes that rolling of the eyes, that suspension of the breath, and that swelling of the heart, which we may all observe, both in ourselves and others, when wondering at some new object, and which are the natural symptoms of uncertain and undetermined thought. What sort of a thing can that be? What is that like? are the questions which, upon such an occasion, we are all naturally disposed to ask. If we can recollect many such objects which exactly resemble this new appearance, and which present themselves to the imagination naturally, and as it were of their own accord, our Wonder is entirely at an end. If we can recollect but a few, and which it requires too some trouble to be able to call up, our Wonder is indeed diminished, but not quite destroyed. If we can recollect none, but are quite at a loss, it is the greatest possible.

With what curious attention does a naturalist examine a singular plant, or a singular fossil, that is presented to him? He is at no loss to refer it to the general genus of plants or fossils; but this does not satisfy him, and when he considers all the different tribes or species of either with which he has hitherto been acquainted, they all, he thinks, refuse to admit the new object among them. It stands alone in his imagination, and as it were detached from all the other species of that genus to which it belongs. He labours, however, to connect it with some one or other of them. Sometimes he thinks it may be placed in this, and sometimes in that other assortment; nor is he ever satisfied, till he has fallen upon one which, in most of its qualities, it resembles. When he cannot do this, rather than it should stand quite by itself, he will enlarge the precincts, if I may say so, of some species, in order to make room for it; or he will create a new species on purpose to receive it, and call it a Play of Nature, or give it some other appellation, under which he arranges all the oddities that he knows not what else to do with. But to some class or other of known objects he must refer it, and betwixt it and them he must find out some resemblance or other, before he can get rid of that Wonder, that uncertainty and anxious curiosity excited by its singular appearance, and by its dissimilitude with all the objects he had hitherto observed.

As single and individual objects thus excite our Wonder when, by their uncommon qualities and singular appearance, they make us uncertain to what species of things we ought to refer them; so a succession of objects which follow one another in an uncommon train or order, will produce the same effect, though there be nothing particular in any one of them taken by itself.

When one accustomed object appears after another, which it does not usually follow, it first excites, by its unexpectedness, the sentiment properly called Surprise, and afterwards, by the singularity of the succession, or order of its appearance, the sentiment properly called Wonder. We start and are surprised at feeling it there, and then wonder how it came there. The motion of a small piece of iron along a plain table is in itself no extraordinary object, yet the person who first saw it begin, without any visible impulse, in consequence of the motion of a loadstone at some little distance from it, could not behold it without the most extreme Surprise; and when that momentary emotion was over, he would still wonder how it came to be conjoined to an event with which, according to the ordinary train of things, he could have so little suspected it to have any connection.

3 When two objects, however unlike, have often been observed to follow each other, and have constantly presented themselves to the senses in that order, they come to be so connected together in the fancy, that the idea of the one seems, of its own accord, to call up and introduce that of the other. If the objects are still observed to succeed each other as before, this connection, or, as it has been called, this association of their ideas, becomes stricter and stricter, and the habit of the imagination to pass from the conception of the one to that of the other, grows more and more rivetted and confirmed. As its ideas move more rapidly than external objects, it is continually running before them, and therefore anticipates, before it happens, every event which falls out according to this ordinary course of things. When objects succeed each other in the same train in which the ideas of the imagination have thus been accustomed to move, and in which, though not conducted by that chain of events presented to the senses, they have acquired a tendency to go on of their own accord, such objects appear all closely connected with one another, and the thought glides easily along them,4 without effort and without interruption. They fall in with the natural career of the imagination; and as the ideas which represented such a train of things would seem all mutually to introduce each other, every last thought to be called up by the foregoing, and to call up the succeeding; so when the objects themselves occur, every last event seems, in the same manner, to be introduced by the foregoing, and to introduce the succeeding. There is no break, no stop, no gap, no interval. The ideas excited by so coherent a chain of things seem, as it were, to float through the mind of their own accord, without obliging it to exert itself, or to make any effort in order to pass from one of them to another.

But if this customary connection be interrupted, if one or more objects appear in an order quite different from that to which the imagination has been accustomed, and for which it is prepared, the contrary of all this happens. We are at first surprised by the unexpectedness5 of the new appearance, and when that momentary emotion is over, we still wonder how it came to occur in that place. The imagination no longer feels the usual facility of passing from the event which goes before to that which comes after. It is an order or law of succession to which it has not been accustomed, and which it therefore finds some difficulty in following, or in attending to. The fancy is stopped and interrupted in that natural movement or career, according to which it was proceeding. Those two events seem to stand at a distance from each other; it endeavours to bring them together, but they refuse to unite; and it feels, or imagines it feels, something like a gap or interval betwixt them. It naturally hesitates, and, as it were, pauses upon the brink of this interval; it endeavours to find out something which may fill up the gap,6 which, like a bridge, may so far at least unite those seemingly distant objects, as to render the passage of the thought betwixt them smooth, and natural, and easy. The supposition of a chain of intermediate, though invisible, events, which succeed each other in a train similar to that in which the imagination has been accustomed to move, and which link together those two disjointed appearances, is the only means by which the imagination can fill up this interval, is the only bridge which, if one may say so, can smooth its passage from the one object to the other. Thus, when we observe the motion of the iron, in consequence of that of the loadstone, we gaze and hesitate, and feel a want of connection betwixt two events which follow one another in so unusual a train. But when, with Des Cartes, we imagine certain invisible effluvia7 to circulate round one of them, and by their repeated impulses to impel the other, both to move towards it, and to follow its motion, we fill up the interval betwixt them, we join them together by a sort of bridge, and thus take off that hesitation and difficulty which the imagination felt in passing from the one to the other. That the iron should move after the loadstone seems, upon this hypothesis, in some measure according to the ordinary course of things. Motion after impulse is an order of succession with which of all things we are the most familiar. Two objects which are so connected seem no longer to be disjoined,8 and the imagination flows smoothly and easily along them.

Such is the nature of this second species of Wonder, which arises from an unusual succession of things. The stop which is thereby given to the career of the imagination, the difficulty which it finds in passing along such disjointed objects, and the feeling of something like a gap or interval betwixt them, constitute the whole essence of this emotion. Upon the clear discovery of a connecting chain of intermediate events, it vanishes altogether. What obstructed the movement of the imagination is then removed. Who wonders at the machinery of the opera–house who has once been admitted behind the scenes? In the Wonders of nature, however, it rarely happens that we can discover so clearly this connecting chain. With regard to a few even of them, indeed, we seem to have been really admitted behind the scenes, and our Wonder accordingly is entirely at an end. Thus the eclipses of the sun and moon, which once, more than all the other appearances in the heavens, excited the terror and amazement of mankind, seem now no longer to be wonderful, since the connecting chain has been found out which joins them to the ordinary course of things. Nay, in those cases in which we have been less successful, even the vague hypotheses of Des Cartes, and the yet more indetermined notions of Aristotle, have, with their followers, contributed to give some coherence to the appearances of nature, and might diminish, though they could not destroy, their Wonder. If they did not completely fill up the interval betwixt the two disjointed objects, they bestowed upon them, however, some sort of loose connection which they wanted before.

That the imagination feels a real difficulty in passing along two events which follow one another in an uncommon order, may be confirmed by many obvious observations. If it attempts to attend beyond a certain time to a long series of this kind, the continual efforts it is obliged to make, in order to pass from one object to another, and thus follow the progress of the succession, soon fatigue it, and if repeated too often, disorder and disjoint its whole frame. It is thus that too severe an application to study sometimes brings on lunacy and frenzy, in those especially who are somewhat advanced in life, but whose imaginations, from being too late in applying, have not got those habits which dispose them to follow easily the reasonings in the abstract sciences. Every step of a demonstration, which to an old practitioner is quite natural and easy, requires from them the most intense application of thought. Spurred on, however, either by ambition, or by admiration for the subject, they still continue till they become, first confused, then giddy, and at last distracted. Could we conceive a person of the soundest judgment, who had grown up to maturity, and whose imagination had acquired those habits, and that mold, which the constitution of things in this world necessarily impress upon it, to be all at once transported alive to some other planet, where nature was governed by laws quite different from those which take place here; as he would be continually obliged to attend to events, which must to him appear in the highest degree jarring, irregular, and discordant, he would soon feel the same confusion and giddiness begin to come upon him, which would at last end in the same manner, in lunacy and distraction. Neither, to produce this effect, is it necessary that the objects should be either great or interesting, or even uncommon, in themselves. It is sufficient that they follow one another in an uncommon order. Let any one attempt to look over even a game of cards, and to attend particularly to every single stroke, and if he is unacquainted with the nature and rules of the game; that is, with the laws which regulate the succession of the cards; he will soon feel the same confusion and giddiness begin to come upon him, which, were it to be continued for days and months, would end in the same manner, in lunacy and distraction. But if the mind be thus thrown into the most violent disorder, when it attends to a long series of events which follow one another in an uncommon train, it must feel some degree of the same disorder, when it observes even a single event fall out in this unusual manner: for the violent disorder can arise from nothing but the too frequent repetition of this smaller uneasiness.

That it is the unusualness alone of the succession which occasions this stop and interruption in the progress of the imagination, as well as the notion of an interval betwixt the two immediately succeeding objects, to be filled up by some chain of intermediate events, is not less evident. The same orders of succession, which to one set of men seem quite according to the natural course of things, and such as require no intermediate events to join them, shall to another appear altogether incoherent and disjointed, unless some such events be supposed: and this for no other reason, but because such orders of succession are familiar to the one, and strange to the other. When we enter the work–houses of the most common artizans; such as dyers, brewers, distillers; we observe a number of appearances, which present themselves in an order that seems to us very strange and wonderful. Our thought cannot easily follow it, we feel an interval betwixt every two of them, and require some chain of intermediate events, to fill it up, and link them together. But the artizan himself, who has been for many years familiar with the consequences of all the operations of his art, feels no such interval. They fall in with what custom has made the natural movement of his imagination: they no longer excite his Wonder, and if he is not a genius superior to his profession, so as to be capable of making the very easy reflection, that those things, though familiar to him, may be strange to us, he will be disposed rather to laugh at, than sympathize with our Wonder. He cannot conceive what occasion there is for any connecting events to unite those appearances, which seem to him to succeed each other very naturally. It is their nature, he tells us, to follow one another in this order, and that accordingly they always do so.9 In the same manner bread has, since the world began, been the common nourishment of the human body, and men have so long seen it, every day, converted into flesh and bones, substances in all respects so unlike it, that they have seldom had the curiosity to inquire by what process of intermediate events this change is brought about. Because the passage of the thought from the one object to the other is by custom become quite smooth and easy, almost without the supposition of any such process. Philosophers, indeed, who often look for a chain of invisible objects to join together two events that occur in an order familiar to all the world, have endeavoured to find out a chain of this kind betwixt the two events I have just now mentioned; in the same manner as they have endeavoured, by a like intermediate chain, to connect the gravity, the elasticity, and even the cohesion of natural bodies, with some of their other qualities. These, however, are all of them such combinations of events as give no stop to the imaginations of the bulk of mankind, as excite no Wonder, nor any apprehension that there is wanting the strictest connection between them. But as in those sounds, which to the greater part of men seem perfectly agreeable to measure and harmony, the nicer ear of a musician will discover a want, both of the most exact time, and of the most perfect coincidence: so the more practised thought of a philosopher, who has spent his whole life in the study of the connecting principles of nature, will often feel an interval betwixt two objects, which, to more careless observers, seem very strictly conjoined. By long attention to all the connections which have ever been presented to his observation, by having often compared them with one another, he has, like the musician, acquired, if one may say so, a nicer ear, and a more delicate feeling with regard to things of this nature. And as to the one, that music seems dissonance which falls short of the most perfect harmony; so to the other, those events seem altogether separated and disjoined, which fall short of the strictest and most perfect connection.

Philosophy is the science of the connecting principles of nature.10 Nature, after the largest experience that common observation can acquire, seems to abound with events which appear solitary and incoherent with all that go before them, which therefore disturb the easy movement of the imagination; which make its ideas succeed each other, if one may say so, by irregular starts and sallies; and which thus tend, in some measure, to introduce those confusions and distractions we formerly mentioned. Philosophy, by representing the invisible chains which bind together all these disjointed objects, endeavours to introduce order into this chaos of jarring and discordant appearances, to allay this tumult of the imagination, and to restore it, when it surveys the great revolutions of the universe, to that tone of tranquillity and composure, which is both most agreeable in itself, and most suitable to its nature. Philosophy, therefore, may be regarded as one of those arts which address themselves to the imagination; and whose theory and history, upon that account, fall properly within the circumference of our subject. Let us endeavour to trace it, from its first origin, up to that summit of perfection to which it is at present supposed to have arrived, and to which, indeed, it has equally been supposed to have arrived in almost all former times. It is the most sublime of all the agreeable arts, and its revolutions have been the greatest, the most frequent, and the most distinguished of all those that have happened in the literary world. Its history, therefore, must, upon all accounts, be the most entertaining and the most instructive. Let us examine, therefore, all the different systems of nature, which, in these western parts of the world, the only parts of whose history we know any thing,11 have successively been adopted by the learned and ingenious; and, without regarding their absurdity or probability, their agreement or inconsistency with truth and reality, let us consider them only in that particular point of view which belongs to our subject; and content ourselves with inquiring how far each of them was fitted to sooth the imagination, and to render the theatre of nature a more coherent, and therefore a more magnificent spectacle, than otherwise it would have appeared to be. According as they have failed or succeeded in this, they have constantly failed or succeeded in gaining reputation and renown to their authors; and this will be found to be the clew that is most capable of conducting us through all the labyrinths of philosophical history: for, in the mean time, it will serve to confirm what has gone before, and to throw light upon what is to come after, that we observe, in general, that no system, how well soever in other respects supported, has ever been able to gain any general credit on the world, whose connecting principles were not such as were familiar to all mankind. Why has the chemical philosophy in all ages crept along in obscurity,12 and been so disregarded by the generality of mankind, while other systems, less useful, and not more agreeable to experience, have possessed universal admiration for whole centuries together? The connecting principles of the chemical philosophy are such as the generality of mankind know nothing about, have rarely seen, and have never been acquainted with; and which to them, therefore, are incapable of smoothing the passage of the imagination betwixt any two seemingly disjointed objects. Salts, sulphurs, and mercuries, acids, and alkalis, are principles13 which can smooth things to those only who live about the furnace; but whose most common operations seem, to the bulk of mankind, as disjointed as any two events which the chemists would connect together by them. Those artists, however, naturally explained things to themselves by principles that were familiar to themselves. As Aristotle observes,14 that the early Pythagoreans, who first studied arithmetic, explained all things by the properties of numbers; and Cicero tells us,15 that Aristoxenus, the musician, found the nature of the soul to consist in harmony. In the same manner, a learned physician lately gave a system of moral philosophy upon the the principles of his own art,16 in which wisdom and virtue were the healthful state of the soul; the different vices and follies, the different diseases to which it was subject; in which the causes and symptoms of those diseases were ascertained; and, in the same medical strain, a proper method of cure prescribed. In the same manner also, others have written parallels of painting and poetry, of poetry and music, of music and architecture, of beauty and virtue, of all the fine arts; systems which have universally owed their origin to the lucubrations of those who were acquainted with the one art, but ignorant of the other; who therefore explained to themselves the phaenomena, in that which was strange to them, by those in that which was familiar; and with whom, upon that account, the analogy, which in other writers gives occasion to a few ingenious similitudes, became the great hinge upon which every thing turned.17

SECTION III

Of the Origin of Philosophy

Mankind, in the first ages of society, before the establishment of law, order, and security, have little curiosity to find out those hidden chains of events which bind together the seemingly disjointed appearances of nature.1 A savage, whose subsistence is precarious, whose life is every day exposed to the rudest dangers, has no inclination to amuse himself with searching out what, when discovered, seems to serve no other purpose than to render the theatre of nature a more connected spectacle to his imagination. Many of these smaller incoherences, which in the course of things perplex philosophers, entirely escape his attention. Those more magnificent irregularities, whose grandeur he cannot overlook, call forth his amazement. Comets, eclipses, thunder, lightning, and other meteors, by their greatness, naturally overawe him, and he views them with a reverence that approaches to fear. His inexperience and uncertainty with regard to every thing about them, how they came, how they are to go, what went before, what is to come after them, exasperate his sentiment into terror and consternation. But our passions, as Father Malbranche observes, all justify themselves;2 that is, suggest to us opinions which justify them. As those appearances terrify him, therefore, he is disposed to believe every thing about them which can render them still more the objects of his terror. That they proceed from some intelligent, though invisible causes, of whose vengeance and displeasure they are either the signs or the effects, is the notion of all others most capable of enhancing this passion, and is that, therefore, which he is most apt to entertain. To this too, that cowardice and pusillanimity, so natural to man in his uncivilized state, still more disposes him; unprotected by the laws of society, exposed, defenceless, he feels his weakness upon all occasions; his strength and security upon none.

But all the irregularities of nature are not of this awful or terrible kind. Some of them are perfectly beautiful and agreeable. These, therefore, from the same impotence of mind, would be beheld with love and complacency, and even with transports of gratitude; for whatever is the cause of pleasure naturally excites our gratitude. A child caresses the fruit that is agreeable to it, as it beats the stone that hurts it.3 The notions of a savage are not very different. The ancient Athenians, who solemnly punished the axe which had accidentally been the cause of the death of a man,4 erected altars, and offered sacrifices to the rainbow. Sentiments not unlike these, may sometimes, upon such occasions, begin to be felt even in the breasts of the most civilized, but are presently checked by the reflection, that the things are not their proper objects. But a savage, whose notions are guided altogether by wild nature and passion, waits for no other proof that a thing is the proper object of any sentiment, than that it excites it. The reverence and gratitude, with which some of the appearances of nature inspire him, convince him that they are the proper objects of reverence and gratitude, and therefore proceed from some intelligent beings, who take pleasure in the expressions of those sentiments. With him, therefore, every object of nature, which by its beauty or greatness, its utility or hurtfulness, is considerable enough to attract his attention, and whose operations are not perfectly regular, is supposed to act by the direction of some invisible and designing power. The sea is spread out into a calm, or heaved into a storm, according to the good pleasure of Neptune. Does the earth pour forth an exuberant harvest? It is owing to the indulgence of Ceres. Does the vine yield a plentiful vintage? It flows from the bounty of Bacchus. Do either refuse their presents? It is ascribed to the displeasure of those offended deities. The tree, which now flourishes, and now decays, is inhabited by a Dryad, upon whose health or sickness its various appearances depend. The fountain, which sometimes flows in a copious, and sometimes in a scanty stream, which appears sometimes clear and limpid, and at other times muddy and disturbed, is affected in all its changes by the Naiad who dwells within it. Hence the origin of Polytheism, and of that vulgar superstition which ascribes all the irregular events of nature to the favour or displeasure of intelligent, though invisible beings, to gods, daemons, witches, genii, fairies. For it may be observed, that in all Polytheistic religions, among savages, as well as in the early ages of Heathen antiquity, it is the irregular events of nature only that are ascribed to the agency and power of their gods. Fire burns, and water refreshes; heavy bodies descend, and lighter substances fly upwards, by the necessity of their own nature; nor was the invisible hand of Jupiter5 ever apprehended to be employed in those matters. But thunder and lightning, storms and sunshine, those more irregular events, were ascribed to his favour, or his anger. Man, the only designing power with which they were acquainted, never acts but either to stop, or to alter the course, which natural events would take, if left to themselves. Those other intelligent beings, whom they imagined, but knew not, were naturally supposed to act in the same manner; not to employ themselves in supporting the ordinary course of things, which went on of its own accord, but to stop, to thwart, and to disturb it. And thus, in the first ages of the world, the lowest and most pusillanimous superstition supplied the place of philosophy.

But when law has established order and security, and subsistence ceases to be precarious, the curiosity of mankind is increased, and their fears are diminished. The leisure which they then enjoy renders them more attentive to the appearances of nature, more observant of her smallest irregularities, and more desirous to know what is the chain which links them all together.6 That some such chain subsists betwixt all her seemingly disjointed phaenomena, they are necessarily led to conceive; and that magnanimity, and cheerfulness, which all generous natures acquire who are bred in civilized societies, where they have so few occasions to feel their weakness, and so many to be conscious of their strength and security, renders them less disposed to employ, for this connecting chain, those invisible beings whom the fear and ignorance of their rude forefathers had engendered.7 Those of liberal fortunes, whose attention is not much occupied either with business or with pleasure, can fill up the void of their imagination, which is thus disengaged from the ordinary affairs of life, no other way than by attending to that train of events which passes around them. While the great objects of nature thus pass in review before them, many things occur in an order to which they have not been accustomed. Their imagination, which accompanies with ease and delight the regular progress of nature, is stopped and embarrassed by those seeming incoherences; they excite their wonder, and seem to require some chain of intermediate events, which, by connecting them with something that has gone before, may thus render the whole course of the universe consistent and of a piece. Wonder, therefore, and not any expectation of advantage from its discoveries, is the first principle which prompts mankind to the study of Philosophy, of that science which pretends to lay open the concealed connections that unite the various appearances of nature; and they pursue this study for its own sake, as an original pleasure or good in itself, without regarding its tendency to procure them the means of many other pleasures.8

Greece, and the Greek colonies in Sicily, Italy, and the Lesser Asia, were the first countries which, in these western parts of the world, arrived at a state of civilized society. It was in them, therefore, that the first philosophers, of whose doctrine we have any distinct account, appeared. Law and order seem indeed to have been established in the great monarchies of Asia and Egypt, long before they had any footing in Greece: yet, after all that has been said concerning the learning of the Chaldeans and Egyptians, whether there ever was in those nations any thing which deserved the name of science, or whether that despotism which is more destructive of security and leisure than anarchy itself, and which prevailed over all the East, prevented the growth of Philosophy, is a question which, for want of monuments, cannot be determined with any degree of precision.9

The Greek colonies having been settled amid nations either altogether barbarous, or altogether unwarlike, over whom, therefore, they soon acquired a very great authority, seem, upon that account, to have arrived at a considerable degree of empire and opulence before any state in the parent country had surmounted that extreme poverty, which, by leaving no room for any evident distinction of ranks, is necessarily attended with the confusion and misrule which flows from a want of all regular subordination.10 The Greek islands being secure from the invasion of land armies, or from naval forces, which were in those days but little known, seem, upon that account too, to have got before the continent in all sorts of civility and improvement. The first philosophers, therefore, as well as the first poets, seem all to have been natives, either of their colonies, or of their islands. It was from thence that Homer, Archilochus, Stesichorus, Simonides, Sappho, Anacreon, derived their birth. Thales and Pythagoras, the founders of the two earliest sects of philosophy, arose, the one in an Asiatic colony, the other in an island; and neither of them established his school in the mother country.11

What was the particular system of either of those two philosophers, or whether their doctrine was so methodized as to deserve the name of a system, the imperfection, as well as the uncertainty of all the traditions that have come down to us concerning them, makes it impossible to determine. The school of Pythagoras, however, seems to have advanced further in the study of the connecting principles of nature, than that of the Ionian philosopher. The accounts which are given of Anaximander, Anaximenes, Anaxagoras, Archelaus, the successors of Thales, represent the doctrines of those sages as full of the most inextricable confusion. Something, however, that approaches to a composed and orderly system, may be traced in what is delivered down to us concerning the doctrine of Empedocles, of Archytas, of Timaeus, and of Ocellus the Lucanian, the most renowned philosophers of the Italian school.12 The opinions of the two last coincide pretty much; the one, with those of Plato; the other, with those of Aristotle; nor do those of the two first seem to have been very different, of whom the one was the author of the doctrine of the Four Elements, the other the inventor of the Categories;13 who, therefore, may be regarded as the founders, the one, of the ancient Physics; the other, of the ancient Dialectic; and, how closely these were connected, will appear hereafter.14 It was in the school of Socrates, however, from Plato and Aristotle, that Philosophy first received that form, which introduced her, if one may say so, to the general acquaintance of the world. It is from them, therefore, that we shall begin to give her history in any detail. Whatever was valuable in the former systems, which was at all consistent with their general principles, they seem to have consolidated into their own. From the Ionian Philosophy, I have not been able to discover that they derived any thing. From the Pythagorean school, both Plato and Aristotle seem to have derived the fundamental principles of almost all their doctrines. Plato, too, appears to have borrowed something from two other sects of philosophers, whose extreme obscurity seems to have prevented them from acquiring themselves any extensive reputation: the one was that of Cratylus and Heraclitus; the other was that of Xenophanes, Parmenides, Melissus, and Zeno.15 To pretend to rescue the system of any of those antesocratic sages, from that oblivion which at present covers them all, would be a vain and useless attempt. What seems, however, to have been borrowed from them, shall sometimes be marked as we go along.

There was still another school of philosophy, earlier than Plato, from which, however, he was so far from borrowing any thing, that he seems to have bent the whole force of his reason to discredit and expose its principles.16 This was the Philosophy of Leucippus, Democritus, and Protagoras,17 which accordingly seems to have submitted to his eloquence, to have lain dormant, and to have been almost forgotten for some generations, till it was afterwards more successfully revived by Epicurus.

SECTION IV

The History of Astronomy

Of all the phaenomena of nature, the celestial appearances are, by their greatness and beauty, the most universal objects of the curiosity of mankind.1 Those who surveyed the heavens with the most careless attention, necessarily distinguished in them three different sorts of objects; the Sun, the Moon, and the Stars. These last, appearing always in the same situation, and at the same distance with regard to one another, and seeming to revolve every day round the earth in parallel circles,2 which widened gradually from the poles to the equator,3 were naturally thought to have all the marks of being fixed, like so many gems, in the concave side of the firmament, and of being carried round by the diurnal revolutions of that solid body: for the azure sky, in which the stars seem to float, was readily apprehended, upon account of the uniformity of their apparent motions, to be a solid body, the roof or outer wall of the universe, to whose inside all those little sparkling objects were attached.

The Sun and Moon, often changing their distance and situation, in regard to the other heavenly bodies, could not be apprehended to be attached to the same sphere with them. They assigned, therefore, to each of them, a sphere of its own; that is, supposed each of them to be attached to the concave side of a solid and transparent body, by whose revolutions they were carried round the earth. There was not indeed, in this case, the same ground for the supposition of such a sphere as in that of the Fixed Stars; for neither the Sun nor the Moon appear to keep always at the same distance with regard to any one of the other heavenly bodies. But as the motion of the Stars had been accounted for by an hypothesis of this kind, it rendered the theory of the heavens more uniform, to account for that of the Sun and Moon in the same manner. The sphere of the Sun they placed above that of the Moon; as the Moon was evidently seen in eclipses to pass betwixt the Sun and the Earth. Each of them was supposed to revolve by a motion of its own, and at the same time to be affected by the motion of the Fixed Stars. Thus, the Sun was carried round from east to west by the communicated movement of this outer sphere, which produced his diurnal revolutions, and the vicissitudes of day and night; but at the same time he had a motion of his own, contrary to this, from west to east, which occasioned his annual revolution, and the continual shifting of his place with regard to the Fixed Stars. This motion was more easy, they thought, when carried on edgeways, and not in direct opposition to the motion of the outer sphere, which occasioned the inclination of the axis of the sphere of the Sun, to that of the sphere of the Fixed Stars; this again produced the obliquity of the ecliptic, and the consequent changes of the seasons. The moon, being placed below the sphere of the Sun, had both a shorter course to finish, and was less obstructed by the contrary movement of the sphere of the Fixed Stars, from which she was farther removed. She finished her period, therefore, in a shorter time, and required but a month, instead of a year, to complete it.

The Stars, when more attentively surveyed, were some of them observed to be less constant and uniform in their motions than the rest, and to change their situations with regard to the other heavenly bodies; moving generally eastwards, yet appearing sometimes to stand still, and sometimes even to move westwards. These, to the number of five, were distinguished by the name of Planets, or wandering Stars, and marked with the particular appellations of Saturn, Jupiter, Mars, Venus, and Mercury. As, like the Sun and Moon, they seem to accompany the motion of the Fixed Stars from east to west, but at the same time to have a motion of their own, which is generally from west to east; they were each of them, as well as those two great lamps of heaven, apprehended to be attached to the inside of a solid concave and transparent sphere, which had a revolution of its own, that was almost directly contrary to the revolution of the outer heaven, but which, at the same time, was hurried along by the superior violence and rapidity of this last.

This is the system of concentric Spheres, the first regular system of Astronomy, which the world beheld, as it was taught in the Italian school4 before Aristotle and his two contemporary philosophers, Eudoxus and Callippus,5 had given it all the perfection which it is capable of receiving. Though rude and inartificial,6 it is capable of connecting together, in the imagination, the grandest and the most seemingly disjointed appearances in the heavens. The motions of the most remarkable objects in the celestial regions, the Sun, the Moon, and the Fixed Stars, are sufficiently connected with one another by this hypothesis. The eclipses of these two great luminaries are, though not so easily calculated, as easily explained, upon this ancient, as upon the modern system. When these early philosophers explained to their disciples the very simple causes of those dreadful phaenomena, it was under the seal of the most sacred secrecy, that they might avoid the fury of the people, and not incur the imputation of impiety, when they thus took from the gods the direction of those events, which were apprehended to be the most terrible tokens of their impending vengeance. The obliquity of the ecliptic, the consequent changes of the seasons, the vicissitudes of day and night, and the different lengths of both days and nights, in the different seasons, correspond too, pretty exactly, with this ancient doctrine. And if there had been no other bodies discoverable in the heavens besides the Sun, the Moon, and the Fixed Stars, this old hypothesis might have stood the examination of all ages, and have gone down triumphant to the remotest posterity.

If it gained the belief of mankind by its plausibility, it attracted their wonder and admiration; sentiments that still more confirmed their belief, by the novelty and beauty of that view of nature which it presented to the imagination. Before this system was taught in the world, the earth was regarded as, what it appears to the eye, a vast, rough, and irregular plain, the basis and foundation of the universe, surrounded on all sides by the ocean, and whose roots extended themselves through the whole of that infinite depth which is below it. The sky was considered as a solid hemisphere, which covered the earth, and united with the ocean at the extremity of the horizon. The Sun, the Moon, and all the heavenly bodies rose out of the eastern, climbed up the convex side of the heavens, and descended again into the western ocean, and from thence, by some subterraneous passages, returned to their first chambers in the east. Nor was this notion confined to the people, or to the poets who painted the opinions of the people: it was held by Xenophanes, the founder of the Eleatic philosophy, after that of the Ionian and Italian schools, the earliest that appeared in Greece. Thales of Miletus too, who, according to Aristotle,7 represented the Earth as floating upon an immense ocean of water, may have been nearly of the same opinion; notwithstanding what we are told by Plutarch8 and Apuleius9 concerning his astronomical discoveries, all of which must plainly have been of a much later date. To those who had no other idea of nature, besides what they derived from so confused an account of things, how agreeable must that system have appeared, which represented the Earth as distinguished into land and water, self–balanced and suspended in the centre of the universe, surrounded by the elements of Air and Ether, and covered by eight polished and cristalline Spheres, each of which was distinguished by one or more beautiful and luminous bodies, and all of which revolved round their common centre, by varied, but by equable and proportionable motions. It seems to have been the beauty of this system that gave Plato10 the notion of something like an harmonic proportion, to be discovered in the motions and distances of the heavenly bodies; and which suggested to the earlier Pythagoreans, the celebrated fancy of the Musick of the Spheres:11 a wild and romantic idea, yet such as does not ill correspond with that admiration, which so beautiful a system, recommended too by the graces of novelty, is apt to inspire.

Whatever are the defects which this account of things labours under, they are such, as to the first observers of the heavens could not readily occur. If all the motions of the Five Planets cannot, the greater part of them may, be easily connected by it; they and all their motions are the least remarkable objects in the heavens; the greater part of mankind take no notice of them at all; and a system, whose only defect lies in the account which it gives of them, cannot thereby be much disgraced in their opinion. If some of the appearances too of the Sun and Moon, the sometimes accelerated and again retarded motions of those luminaries but ill correspond with it; these too, are such as cannot be discovered but by the most attentive observation, and such therefore as we cannot wonder that the imaginations of the first enquirers should slur over, if one may say so, and take little notice of.

It was, however, to remedy those defects, that Eudoxus, the friend and auditor of Plato, found it necessary to increase the number of the Celestial Spheres.12 Each Planet is sometimes observed to advance forward in that eastward course which is peculiar to itself, sometimes to retire backwards, and sometimes again to stand still. To suppose that the Sphere of the Planet should by its own motion, if one may say so, sometimes roll forwards, sometimes roll backwards, and sometimes do neither the one nor the other, is contrary to all the natural propensities of the imagination, which accompanies with ease and delight any regular and orderly motion, but feels itself perpetually stopped and interrupted, when it endeavours to attend to one so desultory and uncertain. It would pursue, naturally and of its own accord, the direct or progressive movement of the Sphere, but is every now and then shocked, if one may say so, and turned violently out of its natural career by the retrograde and stationary appearances of the Planet, betwixt which and its more usual motion, the fancy feels a want of connection, a gap or interval, which it cannot fill up, but by supposing some chain of intermediate events to join them.13 The hypothesis of a number of other spheres revolving in the heavens, besides those in which the luminous bodies themselves were infixed, was the chain with which Eudoxus endeavoured to supply it. He bestowed four of these Spheres upon each of the Five Planets; one in which the luminous body itself revolved, and three others above it. Each of these had a regular and constant, but a peculiar movement of its own, which it communicated to what was properly the Sphere of the Planet, and thus occasioned that diversity of motions observable in those bodies. One of these Spheres, for example, had an oscillatory motion,14 like the circular pendulum of a watch. As when you turn round a watch, like a Sphere upon its axis, the pendulum will, while turned round along with it, still continue to oscillate, and communicate to whatever body is comprehended within it, both its own oscillations and the circular motion of the watch; so this oscillating Sphere, being itself turned round by the motion of the Sphere above it, communicated to the Sphere below it, that circular, as well as its own oscillatory motion; produced by the one, the daily revolutions; by the other, the direct, stationary, and retrograde appearances of the Planet, which derived from a third Sphere that revolution by which it performed its annual period. The motions of all these Spheres were in themselves constant and equable, such as the imagination could easily attend to and pursue, and which connected together that otherwise incoherent diversity of movements observable in the Sphere of the Planet. The motions of the Sun and Moon being more regular than those of the Five Planets, by assigning three Spheres to each of them, Eudoxus imagined he could connect together all the diversity of movements discoverable in either. The motion of the Fixed Stars being perfectly regular, one Sphere he judged sufficient for them all. So that, according to this account, the whole number of Celestial Spheres amounted to twenty–seven. Callippus, though somewhat younger, the cotemporary of Eudoxus, found that even this number was not enough to connect together the vast variety of movements which he discovered in those bodies, and therefore increased it to thirty–four.15 Aristotle, upon a yet more attentive observation, found that even all these Spheres would not be sufficient, and therefore added twenty–two more, which increased their number to fifty–six.16 Later observers discovered still new motions, and new inequalities, in the heavens. New Spheres were therefore still to be added to the system, and some of them to be placed even above that of the Fixed Stars. So that in the sixteenth century, when Fracostorio,17 smit with the eloquence of Plato and Aristotle, and with the regularity and harmony of their system, in itself perfectly beautiful, though it corresponds but inaccurately with the phaenomena, endeavoured to revive this ancient Astronomy, which had long given place to that of Ptolemy and Hipparchus,18 he found it necessary to multiply the number of Celestial Spheres to seventy–two; neither were all these enough.

This system had now become as intricate and complex as those appearances themselves, which it had been invented to render uniform and coherent. The imagination, therefore, found itself but little relieved from that embarrassment, into which those appearances had thrown it, by so perplexed an account of things. Another system, for this reason, not long after the days of Aristotle, was invented by Apollonius,19 which was afterwards perfected by Hipparchus, and has since been delivered down to us by Ptolemy, the more artificial system of Eccentric Spheres and Epicycles.20

In this system, they first distinguished betwixt the real and apparent motion of the heavenly bodies. These, they observed, upon account of their immense distance, must necessarily appear to revolve in circles concentric with the globe of the Earth, and with one another: but that we cannot, therefore, be certain that they really revolve in such circles, since, though they did not, they would still have the same appearance. By supposing, therefore, that the Sun and the other Planets revolved in circles, whose centres were very distant from the centre of the Earth; that consequently, in the progress of their revolution, they must sometimes approach nearer, and sometimes recede further from it, and must, therefore, to its inhabitants appear to move faster in the one case, and slower in the other, those philosophers imagined they could account for the apparently unequal velocities of all those bodies.

By supposing, that in the solidity of the Sphere of each of the Five Planets there was formed another little Sphere, called an Epicycle, which revolved round its own centre, at the same time that it was carried round the centre of the Earth by the revolution of the great Sphere, betwixt whose concave and convex sides it was inclosed; in the same manner as we might suppose a little wheel inclosed within the outer circle of a great wheel, and which whirled about several times upon its own axis, while its centre was carried round the axis of the great wheel, they imagined they could account for the retrograde and stationary appearances of those most irregular objects in the heavens. The Planet, they supposed, was attached to the circumference, and whirled round the centre of this little Sphere,21 at the same time that it was carried round the Earth by the movement of the great Sphere. The revolution of this little Sphere, or Epicycle, was such, that the Planet, when in the upper part of it; that is, when furthest off and least sensible to the eye; was carried round in the same direction with the centre of the Epicycle, or with the Sphere in which the Epicycle was inclosed: but when in the lower part, that is, when nearest and most sensible to the eye; it was carried round in a direction contrary to that of the centre of the Epicycle: in the same manner as every point in the upper part of the outer circle of a coach–wheel revolves forward in the same direction with the axis, while every point, in the lower part, revolves backwards in a contrary direction to the axis. The motions of the Planet, therefore, surveyed from the Earth appeared direct, when in the upper part of the Epicycle, and retrograde, when in the lower. When again it either descended from the upper part to the lower, or ascended from the lower to the upper, it necessarily appeared stationary.

But, though, by the eccentricity of the great Sphere, they were thus able, in some measure, to connect together the unequal velocities of the heavenly bodies, and by the revolutions of the little Sphere, the direct, stationary, and retrograde appearances of the Planets, there was another difficulty that still remained. Neither the Moon, nor the three superior Planets, appear always in the same part of the heavens, when at their periods of most retarded motion, or when they are supposed to be at the greatest distance from the Earth. The apogeum therefore, or the point of greatest distance from the Earth, in the Spheres of each of those bodies, must have a movement of its own, which may carry it successively through all the different points of the Ecliptic. They supposed, therefore, that while the great eccentric Sphere revolved eastwards round its centre, that its centre too revolved westwards in a circle of its own, round the centre of the Earth, and thus carried its apogeum through all the different points of the Ecliptic.

But with all those combined and perplexed circles; though the patrons of this system were able to give some degree of uniformity to the real directions of the Planets, they found it impossible so to adjust the velocities of those supposed Spheres to the phaenomena, as that the revolution of any one of them, when surveyed from its own centre, should appear perfectly equable and uniform. From that point, the only point in which the velocity of what moves in a circle can be truly judged of, they would still appear irregular and inconstant, and such as tended to embarrass and confound the imagination. They invented, therefore, for each of them, a new Circle, called the Equalizing Circle, from whose centre they should all appear perfectly equable: that is, they so adjusted the velocities of these Spheres, as that, though the revolution of each of them would appear irregular when surveyed from its own centre, there should, however, be a point comprehended within its circumference, from whence its motions should appear to cut off, in equal times, equal portions of the Circle, of which that point was the centre.

Nothing can more evidently show, how much the repose and tranquillity of the imagination is the ultimate end of philosophy, than the invention of this Equalizing Circle. The motions of the heavenly bodies had appeared inconstant and irregular, both in their velocities and in their directions. They were such, therefore, as tended to embarrass and confound the imagination, whenever it attempted to trace them. The invention of Eccentric Spheres, of Epicycles, and of the revolution of the centres of the Eccentric Spheres, tended to allay this confusion, to connect together those disjointed appearances, and to introduce harmony and order into the mind’s conception of the movements of those bodies. It did this, however, but imperfectly; it introduced uniformity and coherence into their real directions. But their velocities, when surveyed from the only point in which the velocity of what moves in a Circle can be truly judged of, the centre of that Circle, still remained, in some measure, inconstant as before; and still, therefore, embarrassed the imagination. The mind found itself somewhat relieved from this embarrassment, when it conceived, that how irregular soever the motions of each of those Circles might appear, when surveyed from its own centre, there was, however, in each of them, a point, from whence its revolution would appear perfectly equable and uniform, and such as the imagination could easily follow. Those philosophers transported themselves, in fancy, to the centres of these imaginary Circles, and took pleasure in surveying from thence, all those fantastical motions, arranged, according to that harmony and order, which it had been the end of all their researches to bestow upon them. Here, at last, they enjoyed that tranquillity and repose which they had pursued through all the mazes of this intricate hypothesis; and here they beheld this, the most beautiful and magnificent part of the great theatre of nature, so disposed and constructed, that they could attend, with ease and delight, to all the revolutions and changes that occurred in it.

These, the System of Concentric, and that of Eccentric Spheres, seem to have been the two Systems of Astronomy, that had most credit and reputation with that part of the ancient world, who applied themselves particularly to the study of the heavens. Cleanthes,22 however, and the other philosophers of the Stoical sect who came after him, appear to have had a system of their own, quite different from either. But, though justly renowned for their skill in dialectic, and for the security and sublimity of their moral doctrines, those sages seem never to have had any high reputation for their knowledge of the heavens; neither is the name of any one of them23 ever counted in the catalogue of the great astronomers, and studious observers of the Stars, among the ancients. They rejected the doctrine of the Solid Spheres; and maintained, that the celestial regions were filled with a fluid ether, of too yielding a nature to carry along with it, by any motion of its own, bodies so immensely great as the Sun, Moon, and Five Planets. These, therefore, as well as the Fixed Stars, did not derive their motion from the circumambient body, but had each of them, in itself, and peculiar to itself, a vital principle of motion, which directed it to move with its own peculiar velocity, and its own peculiar direction. It was by this internal principle, that the Fixed Stars revolved directly from east to west in circles parallel to the Equator, greater or less, according to their distance or nearness to the Poles, and with velocities so proportioned, that each of them finished its diurnal period in the same time, in something less than twenty–three hours and fifty–six minutes. It was, by a principle of the same kind, that the Sun moved westwards, for they allowed of no eastward motion in the heavens, but with less velocity than the Fixed Stars, so as to finish his diurnal period in twenty–four hours, and, consequently, to fall every day behind them, by a space of the heavens nearly equal to that which he passes over in four minutes; that is, nearly equal to a degree. This revolution of the Sun, too, was neither directly westwards, nor exactly circular; but after the Summer Solstice, his motion began gradually to incline a little southwards, appearing in his meridian to–day, further south than yesterday; and to–morrow still further south than to–day; and thus continuing every day to describe a spiral line round the Earth, which carried him gradually further and further southwards, till he arrived at the Winter Solstice. Here, this spiral line began to change its direction, and to bring him gradually, every day, further and further northwards, till it again restored him to the Summer Solstice. In the same manner they accounted for the motion of the Moon, and that of the Five Planets, by supposing that each of them revolved westwards, but with directions, and velocities, that were both different from one another, and continually varying; generally, however, in spherical lines, somewhat inclined to the Equator.

This system seems never to have had the vogue. The system of Concentric as well as that of Eccentric Spheres gives some sort of reason, both for the constancy and equability of the motion of the Fixed Stars, and for the variety and uncertainty of that of the Planets. Each of them bestow some sort of coherence upon those apparently disjointed phaenomena. But this other system seems to leave them pretty much as it found them. Ask a Stoic, why all the Fixed Stars perform their daily revolutions in circles parallel to each other, though of very different diameters, and with velocities so proportioned, that they all finish their period at the same time, and through the whole course of it preserve the same distance and situation with regard to one another? He can give no other answer, but that the peculiar nature, or if one may say so, the caprice of each Star24 directs it to move in that peculiar manner. His system affords him no principle of connection, by which he can join together, in his imagination, so great a number of harmonious revolutions. But either of the other two systems, by the supposition of the solid firmament, affords this easily. He is equally at a loss to connect together the peculiarities that are observed in the motions of the other heavenly bodies; the spiral motion of them all; their alternate progression from north to south, and from south to north; the sometimes accelerated, and again retarded motions of the Sun and Moon; the direct retrograde and stationary appearances of the Planets. All these have, in his system, no bond of union, but remain as loose and incoherent in the fancy, as they at first appeared to the senses, before philosophy had attempted, by giving them a new arrangement, by placing them at different distances, by assigning to each some peculiar but regular principle of motion, to methodize and dispose them into an order that should enable the imagination to pass as smoothly, and with as little embarrassment, along them, as along the most regular, familiar, and coherent appearances of nature.

Such were the systems of Astronomy that, in the ancient world, appear to have been adopted by any considerable party. Of all of them, the system of Eccentric Spheres was that which corresponded most exactly with the appearances of the heavens. It was not invented till after those appearances had been observed, with some accuracy, for more than a century together; and it was not completely digested by Ptolemy till the reign of Antoninus,25 after a much longer course of observations. We cannot wonder, therefore, that it was adapted to a much greater number of the phaenomena, than either of the other two systems, which had been formed before those phaenomena were observed with any degree of attention, which, therefore, could connect them together only while they were thus regarded in the gross, but which, it could not be expected, should apply to them when they came to be considered in the detail. From the time of Hipparchus, therefore, this system seems to have been pretty generally received by all those who attended particularly to the study of the heavens. That astronomer first made a catalogue of the Fixed Stars;26 calculated, for six hundred years, the revolutions of the Sun, Moon, and Five Planets; marked the places in the heavens, in which, during all that period, each of those bodies should appear; ascertained the times of the eclipses of the Sun and Moon, and the particular places of the Earth in which they should be visible. His calculations were founded upon this system, and as the events corresponded to his predictions, with a degree of accuracy which, though inferior to what Astronomy has since arrived at, was greatly superior to any thing which the world had then known, they ascertained, to all astronomers and mathematicians, the preference of his system, above all those which had been current before it.

It was, however, to astronomers and mathematicians only, that they ascertained this; for, notwithstanding the evident superiority of this system, to all those with which the world was then acquainted, it was never adopted by any one sect of philosophers.

Philosophers, long before the days of Hipparchus, seem to have abandoned the study of nature,27 to employ themselves chiefly in ethical, rhetorical, and dialectical questions.28 Each party of them too, had by this time completed their peculiar system or theory of the universe, and no human consideration could then have induced them to give up any part of it. That supercilious and ignorant contempt too, with which at this time they regarded all mathematicians, among whom they counted astronomers, seems even to have hindered them from enquiring so far into their doctrines, as to know what opinions they held. Neither Cicero nor Seneca, who have so often occasion to mention the ancient systems of Astronomy, take any notice of that of Hipparchus. His name is not to be found in the writings of Seneca. It is mentioned but once in those of Cicero, in a letter to Atticus,29 but without any note of approbation, as a geographer, and not as an astronomer. Plutarch, when he counts up, in his second book, concerning the opinions of philosophers, all the ancient systems of Astronomy,30 never mentions this, the only tolerable one which was known in his time. Those three authors, it seems, conversed only with the writings of philosophers. The elder Pliny31 indeed, a man whose curiosity extended itself equally to every part of learning, describes the system of Hipparchus, and never mentions its author, which he has occasion to do often, without some note of that high admiration which he had so justly conceived for his merit. Such profound ignorance32 in those professed instructors of mankind, with regard to so important a part of the learning of their own times, is so very remarkable, that I thought it deserved to be taken notice of, even in this short account of the revolutions of philosophy.

Systems in many respects resemble machines.33 A machine is a little system, created to perform, as well as to connect together, in reality, those different movements and effects which the artist has occasion for. A system is an imaginary machine invented to connect together in the fancy those different movements and effects which are already in reality performed. The machines that are first invented to perform any particular movement are always the most complex, and succeeding artists generally discover that, with fewer wheels, with fewer principles of motion, than had originally been employed, the same effects may be more easily produced.34 The first systems, in the same manner, are always the most complex, and a particular connecting chain, or principle, is generally thought necessary to unite every two seemingly disjointed appearances: but it often happens, that one great connecting principle is afterwards found to be sufficient to bind together all the discordant phaenomena that occur in a whole species of things. How many wheels are necessary to carry on the movements of this imaginary machine, the system of Eccentric Spheres! The westward diurnal revolution of the Firmament, whose rapidity carries all the other heavenly bodies along with it, requires one. The periodical eastward revolutions of the Sun, Moon, and Five Planets, require, for each of those bodies, another. Their differently accelerated and retarded motions require, that those wheels, or circles, should neither be concentric with the Firmament, nor with one another; which, more than any thing, seems to disturb the harmony of the universe. The retrograde and stationary appearance of the Five Planets, as well as the extreme inconstancy of the Moon’s motion, require, for each of them, an Epicycle, another little wheel attached to the circumference of the great wheel, which still more interrupts the uniformity of the system. The motion of the apogeum of each of those bodies requires, in each of them, still another wheel, to carry the centres of their Eccentric Spheres round the centre of the Earth. And thus, this imaginary machine, though, perhaps, more simple, and certainly better adapted to the phaenomena than the Fifty–six Planetary Spheres of Aristotle, was still too intricate and complex for the imagination to rest in it with complete tranquillity and satisfaction.

It maintained its authority, however, without any diminution of reputation, as long as science was at all regarded in the ancient world. After the reign of Antoninus, and, indeed, after the age of Hipparchus, who lived almost three hundred years before Antoninus, the great reputation which the earlier philosophers had acquired, so imposed upon the imaginations of mankind, that they seem to have despaired of ever equalling their renown. All human wisdom, they supposed, was comprehended in the writings of those elder sages. To abridge, to explain, and to comment upon them, and thus show themselves, at least, capable of understanding some of their sublime mysteries, became now the only probable road to reputation. Proclus and Theon wrote commentaries upon the System of Ptolemy;35 but, to have attempted to invent a new one, would then have been regarded, not only as presumption, but as impiety to the memory of their so much revered predecessors.

The ruin of the empire of the Romans, and, along with it, the subversion of all law and order, which happened a few centuries afterwards, produced the entire neglect of that study of the connecting principles of nature, to which leisure and security can alone give occasion.36 After the fall of those great conquerors and civilizers of mankind, the empire of the Califfs seems to have been the first state under which the world enjoyed that degree of tranquillity which the cultivation of the sciences requires. It was under the protection of those generous and magnificent princes, that the ancient philosophy and astronomy of the Greeks were restored and established in the East; that tranquillity, which their mild,37 just, and religious government diffused over their vast empire, revived the curiosity of mankind, to inquire into the connecting principles of nature. The fame of the Greek and Roman learning, which was then recent in the memories of men, made them desire to know, concerning these abstruse subjects, what were the doctrines of the so much renowned sages of those two nations.

They translated, therefore, into the Arabian language, and studied, with great eagerness, the works of many Greek philosophers, particularly of Aristotle, Ptolemy, Hippocrates, and Galen.38 The superiority which they easily discovered in them, above the rude essays which their own nation39 had yet had time to produce, and which were such, we may suppose, as arise every where in the first infancy of science, necessarily determined them to embrace their systems, particularly that of Astronomy: neither were they ever afterwards able to throw off their authority. For, though the munificence of the Abassides, the second race of the Califfs, is said to have supplied the Arabian astronomers with larger and better instruments, than any that were known to Ptolemy and Hipparchus, the study of the sciences seems, in that mighty empire, to have been either of too short, or too interrupted a continuance, to allow them to make any considerable correction in the doctrines of those old mathematicians. The imaginations of mankind had not yet got time to grow so familiar with the ancient systems, as to regard them without some degree of that astonishment which their grandeur and novelty excited; a novelty of a peculiar kind, which had at once the grace of what was new, and the authority of what was ancient. They were still, therefore, too much enslaved to those systems, to dare to depart from them, when those confusions which shook, and at last overturned the peaceful throne of the Califfs, banished the study of the sciences from that empire. They had, however, before this, made some considerable improvements: they had measured the obliquity of the Ecliptic, with more accuracy than had been done before. The tables of Ptolemy had, by the length of time, and by the inaccuracy of the observations upon which they were founded, become altogether wide of what was the real situation of the heavenly bodies, as he himself indeed had foretold they would do. It became necessary, therefore, to form new ones, which was accordingly executed by the orders of the Califf Almamon,40 under whom, too, was made the first mensuration of the Earth that we know of, after the commencement of the Christian Aera, by two Arabian astronomers, who, in the plain of Sennaar,41 measured two degrees of its circumference.

The victorious arms of the Saracens carried into Spain the learning, as well as the gallantry, of the East; and along with it, the tables of Almamon, and the Arabian translations of Ptolemy and Aristotle; and thus Europe received a second time, from Babylon, the rudiments of the science of the heavens. The writings of Ptolemy were translated from Arabic into Latin;42 and the Peripatetic philosophy was studied in Averroes and Avicenna with as much eagerness, and with as much submission to its doctrines in the West, as it had been in the East.43

The doctrine of the Solid Spheres had, originally, been invented, in order to give a physical account of the revolutions of the heavenly bodies, according to the system of Concentric Circles, to which that doctrine was very easily accommodated. Those mathematicians who invented the doctrine of Eccentric Circles and Epicycles, contented themselves with showing, how, by supposing the heavenly bodies to revolve in such orbits, the phaenomena might be connected together, and some sort of uniformity and coherence be bestowed upon their real motions. The physical causes of those motions they left to the consideration of the philosophers; though, as appears from some passages of Ptolemy, they had some general apprehension, that they were to be explained by a like hypothesis. But, though the system of Hipparchus44 was adopted by all astronomers and mathematicians, it never was received, as we have already observed, by any one sect of philosophers among the ancients. No attempt, therefore, seems to have been made amongst them, to accommodate to it any such hypothesis.

The schoolmen, who received, at once, from the Arabians, the philosophy of Aristotle, and the astronomy of Hipparchus, were necessarily obliged to reconcile them to one another, and to connect together the revolutions of the Eccentric Circles and Epicycles of the one, by the solid Spheres of the other. Many different attempts of this kind were made by many different philosophers: but, of them all, that of Purbach,45 in the fifteenth century, was the happiest and the most esteemed. Though his hypothesis is the simplest of any of them, it would be in vain to describe it without a scheme; neither is it easily intelligible with one: for, if the system of Eccentric Circles and Epicycles was before too perplexed and intricate for the imagination to rest in it, with complete tranquillity and satisfaction, it became much more so, when this addition had been made to it. The world, justly indeed, applauded the ingenuity of that philosopher, who could unite, so happily, two such seemingly inconsistent systems. His labours, however, seem rather to have increased than to have diminished the causes of that dissatisfaction, which the learned soon began to feel with the system of Ptolemy. He, as well as all those who had worked upon the same plan before him, by rendering this account of things more complex, rendered it still more embarrassing than it had been before.

Neither was the complexness of this system the sole cause of the dissatisfaction, which the world in general began, soon after the days of Purbach, to express for it. The tables of Ptolemy having, upon account of the inaccuracy of the observations on which they were founded, become altogether wide of the real situation of the heavenly bodies, those of Almamon,46 in the ninth century, were, upon the same hypothesis, composed to correct their deviations. These again, a few ages afterwards, became, for the same reason, equally useless. In the thirteenth century, Alphonsus, the philosophical king of Castile,47 found it necessary to give orders for the composition of those tables, which bear his name. It is he, who is so well known for the whimsical impiety of using to say, that, had he been consulted at the creation of the universe, he could have given good advice; an apophthegm which is supposed to have proceeded from his dislike to the intricate system of Ptolemy. In the fifteenth century, the deviation of the Alphonsine tables began to be as sensible, as those of Ptolemy and Almamon had been before. It appeared evident, therefore, that, though the system of Ptolemy might, in the main, be true, certain corrections were necessary to be made in it before it could be brought to correspond with exact precision to the phaenomena.48 For the revolution of his Eccentric Circles and Epicycles, supposing them to exist, could not, it was evident, be precisely such as he represented them; since the revolutions of the heavenly bodies deviated, in a short time, so widely from what the most exact calculations, that were founded upon his hypothesis, represented them. It had plainly, therefore, become necessary to correct, by more accurate observations, both the velocities and directions of all the wheels and circles of which his hypothesis is composed. This, accordingly, was begun by Purbach, and carried on by Regiomontanus,49 the disciple, the continuator, and the perfecter of the system of Purbach; and one, whose untimely death, amidst innumerable projects for the recovery of old, and the invention and advancement of new sciences, is, even at this day, to be regretted.

When you have convinced the world, that an established system ought to be corrected, it is not very difficult to persuade them that it should be destroyed. Not long, therefore, after the death of Regiomontanus, Copernicus began to meditate a new system, which should connect together the celestial appearances, in a more simple as well as a more accurate manner, than that of Ptolemy.

The confusion, in which the old hypothesis represented the motions of the heavenly bodies, was, he tells us,50 what first suggested to him the design of forming a new system, that these, the noblest works of nature, might no longer appear devoid of that harmony and proportion which discover themselves in her meanest productions. What most of all dissatisfied him, was, the motion of the Equalizing Circle, which, by representing the revolutions of the Celestial Spheres, as equable only, when surveyed from a point that was different from their centers, introduced a real inequality into their motions; contrary to that most natural, and indeed fundamental idea, with which all the authors of astronomical systems, Plato, Eudoxus, Aristotle, even Hipparchus and Ptolemy themselves, had hitherto set out, that the real motions of such beautiful and divine objects must necessarily be perfectly regular, and go on, in a manner, as agreeable to the imagination, as the objects themselves are to the senses. He began to consider, therefore, whether, by supposing the heavenly bodies to be arranged in a different order from that in which Aristotle and Hipparchus had placed them, this so much sought for uniformity might not be bestowed upon their motions. To discover this arrangement, he examined all the obscure traditions delivered down to us, concerning every other hypothesis which the ancients had invented, for the same purpose. He found, in Plutarch,51 that some old Pythagoreans had represented the Earth as revolving in the centre of the universe, like a wheel round its own axis; and that others, of the same sect, had removed it from the centre, and represented it as revolving in the Ecliptic like a star round the central fire. By this central fire, he supposed they meant the Sun; and though in this he was very widely mistaken,