Front Page Titles (by Subject) CHAPTER XXIV.: THE RELATION OF SEQUENCE. - The Principles of Psychology
The Online Library of Liberty
A project of Liberty Fund, Inc.
CHAPTER XXIV.: THE RELATION OF SEQUENCE. - Herbert Spencer, The Principles of Psychology 
The Principles of Psychology (London: Longman, Brown, Green and Longmans, 1855).
About Liberty Fund:
Liberty Fund, Inc. is a private, educational foundation established to encourage the study of the ideal of a society of free and responsible individuals.
The text is in the public domain.
Fair use statement:
This material is put online to further the educational goals of Liberty Fund, Inc. Unless otherwise stated in the Copyright Information section above, this material may be used freely for educational and academic purposes. It may not be used in any way for profit.
THE RELATION OF SEQUENCE.
§ 96. As was said in the last chapter, this remaining relation is but another side of the fundamental one there treated of. Sequence is change; and change, as known by us, is the unlikeness of a present state of consciousness to a past state. While on the one hand, the two terms of a relation of unlikeness cannot be known without a change in consciousness; on the other hand, there can be no change in consciousness without there being two states standing in a relation of unlikeness. The fundamental, the undecomposable relation must have two terms—two adjacent states of consciousness. If these are thought of in themselves, they must be thought of as unlike; otherwise they will constitute not two states but one. If they are thought of as states of consciousness, they must be thought of as constituting a sequence; seeing that consciousness cannot be in two states at one time. The ultimate relation, therefore, is nothing more than a change in the state of consciousness: and we call it either a relation of unlikeness or a relation of sequence, according as we think of the contrast between the antecedent and consequent states, or of their order.
Beyond thus describing each aspect of this relation in terms of the other, no account can be given of it. Like every primordial experience—like the sensation of redness or that of warmth, it transcends analysis. All that can be done is to divide the relations of sequence into their respective classes; and to inquire in what manner these are distinguished from one another in consciousness. To do this completely, is by no means easy; and would moreover occupy more space than can here be afforded. It must suffice to describe the leading distinctions, so far as is requisite to show their harmony with the general results of the analysis.
§ 97. It is tolerably manifest that these distinctions cannot be originally given in the consciousness of the sequences themselves. By a nascent intelligence, the relation between two sensations that severally answer to some external cause and effect, cannot be known as different in nature from that between two sensations that follow one another fortuitously. In so far as its incipient experience is concerned, there is no difference. The two relations are two changes in consciousness, and nothing more. If then, some changes, some sequences, are afterwards found to be of a different quality from others, it must be in virtue of a collateral property additional to the succession itself—a collateral property disclosed by further experience. What is that property?
The comparison of a few cases will indicate the answer to this question. After hearing in immediate succession two notes of different pitch, not the least difficulty is found in making those notes—or rather, the ideas of them—pass through consciousness in the reverse order. After an ascending fifth has been struck upon the piano, it is easy so to represent the sounds to the mind as to make a descending fifth. That is to say, the two states of consciousness produced may readily be re-thought in inverted sequence. Not that the two states thus voluntarily changed in their order, are entirely like the original states. Though they are like in nature, they are widely unlike in intensity. While the original states, which we know as two sensations of sound, are vivid, the two ideas which we find may be reversed in succession, are but very faint repetitions of them. And this it is which distinguishes one of these reversable sequences from a coexistence. If the successive states of consciousness A, B, will occur in the opposite order B, A, without any diminution of vividness, the relation between them is that which we know as coexistence. But if the states A, B, when they occur in opposite order, do so only as the weak states B, A, the relation between them is that of reversable sequence. Thus much to prevent misapprehension. What it now concerns us to observe, is, that there are sequences whose terms having been presented to consciousness in one order, admit of being represented to consciousness in the opposite order with great facility. Not that they occur in this opposite order with as much facility as in the original order. Two impressions that were experienced in a certain succession, tend, when recalled, to pass through consciousness in a like succession; and it is in virtue of their tendency to do this, that we know them to have occurred in that succession; or rather, it is their recurrence in this succession which constitutes our knowledge of their original succession. But though, when uninterfered with by the will, the represented impressions follow one another in an order like that in which the presented ones followed; yet, in cases such as the one instanced, the slightest effort of volition suffices to reverse the order—an effort so slight as to be unaccompanied by any sense of tension. That some effort is required, is to be inferred from the fact that while the represented impressions involuntarily follow one another in the original order, they do not follow in the opposite one, unless voluntarily. But this is the sole appreciable distinction. Thus, then, we find that there is a certain order of sequences which have the peculiarity, that they may be represented to consciousness in reverse order with but a nominal effort. And these are the sequences which, objectively considered, we class as accidental.
But if, instead of two phenomena that have occurred in a merely fortuitous succession, or in a succession whose genesis is so complex as to seem fortuitous to us, we take two phenomena which occur in a certain order with considerable regularity, and examine the relation subsisting between the states of consciousness severally answering to them, we shall find it to be of a somewhat different quality. Take, for example, the shouting to any one, and the turning of his head. Frequently as these two phenomena have been known to us in this order, the occurrence of the one almost inevitably suggests the other. If the first be presented to consciousness, it is only by an effort that the other can be prevented from following it. Moreover, the impressions have no tendency to pass through consciousness in the opposite order. The turning of another person's head, does not make us think of a shout. Nevertheless, there is little or no difficulty in reversing the order of these states. The thought of a person turning his head, may be instantly followed in consciousness by the thought of a shout. Sequences of this kind then, are distinguished by the peculiarity that though, when the antecedent is presented or represented in consciousness, a representation of the consequent cannot without difficulty be prevented from rising; yet these two states can readily have their order of succession changed. And this is the character of the sequences which, objectively considered, we class as probable.
When, however, we pass from non-necessary sequences to necessary sequences, we not only find that the states of consciousness are so connected that when the antecedent is presented, it is next to impossible, if not impossible, to prevent the consequent following it; but we find that the antecedent and consequent do not admit of transposition. As an illustration of the first peculiarity, may be taken our inability to think of a heavy weight as breaking the string by which it is suspended, without thinking of the weight as falling. And the last peculiarity is illustrated in the fact, that the relation between a blow and an antecedent motion, cannot be represented to the mind in the reverse order.
§ 98. Thus then, the relation of sequence, considered subjectively as simply a change in consciousness, is of three general kinds. The fortuitous, in which the two terms are as nearly as may be alike in their tendency, or want of tendency, subsequently to suggest each other; and in which the change may be reversed in thought, with a feeling of non-resistance like that with which it originally occurred. The probable, in which the terms are unlike in their tendency to suggest each other; but in which the usual order of the terms may readily be inverted. And the necessary, in which the antecedent being presented or represented to consciousness, the consequent cannot be prevented from following; and in which the direction of the change cannot be changed.
This statement, imperfect as it is, and requiring though it does much to be said in explanation of difficulties that may be suggested, will serve to show, what it here chiefly concerns us to note, that the classification of sequences is itself effected through other sequences. The classification, depending as it does upon the different modes in which the sequences comport themselves when tested, involves, in the outset, the ideas of like and unlike; while the process of testing them, is itself an observing of the degrees of likeness or unlikeness between certain feelings which they severally yield under experiment. And as the relations of likeness and unlikeness are the one a double, and the other a single sequence, it results that the classing of sequences implies the making them the terms of secondary sequences. As all the relations are finally reducible to one, which is nothing else than a change in consciousness, it follows, even à priori, that all relations among the changes in consciousness must themselves be other changes.