PSYCHOLOGY 57 as part of a larger thing or as itself compounded of such parts which has had one beginning in time. But what is it that has thus a beginning and continues indefinitely ? This leads to our last point. Jubstau- (e^ go far we have been concerned only with the com- iality. bination of sensory and motor presentations into groups and with the differentiation of group from group; the relations to each other of the constituents of each group still for the most part remain. To these relations in the main must be referred the correlative conceptions of sub- stance and attribute, the distinction in substances of qualities and powers, of primary qualities and secondary, and the like. 1 Of all the constituents of things only one is universally present, that above described as physical solidity, which presents itself according to circumstances as impenetrability, resistance, or weight. Things differing in temperature, colour, taste, and smell agree in resisting compression, in filling space. Because of this quality we regard the wind as a thing, though it has neither shape nor colour, while a shadow, though it has both but not resistance, is the very type of nothingness. This constituent is invariable, while other qualities are either absent or change, form altering, colour disappearing with light, sound and smells intermitting. Many of the other qualities colour, tem- perature, sound, smell increase in intensity until we reach and touch a body occupying space ; with the same move- ment too its visual magnitude varies. At the moment of contact an unvarying tactual magnitude is ascertained, while the other qualities and the visual magnitude reach a fixed maximum ; then first it becomes possible by effort to change or attempt to change the position and form of what we apprehend. This tangible plenum we thence- forth regard as the seat and source of all the qualities we project into it. In other words, that which occupies space is psychologically the substantial ; the other real consti- tuents are but its properties or attributes, the marks or manifestations which lead us to expect its presence. Imagination or Ideation. npres- Before the intuition of things has reached a stage so " s complete and definite as that just described, imagination leag or ideation as distinct from perception has well begun. In passing to the consideration of this higher form of mental life we have to note the distinction between im- pressions and images or ideas, to which Hume first gave general currency. Hume did not think it " necessary to employ many words in explaining this distinction. Every one of himself will readily perceive the difference . . . ; though it is not impossible but in particular instances they may very nearly approach to each other. Thus in sleep, in a fever, in madness, or in any very violent emotions of soul, our ideas may approach to our impressions ; as, on the other hand, it sometimes happens our impressions are so faint and low that we cannot distinguish them from our ideas." 2 In most cases, no doubt, the obvious differ- ence in intensity, or, as Hume puts it, "in the force or liveliness with which they strike upon the mind," is a sufficient characteristic, but we must examine a good deal further and pay more attention to his uncertain cases if this important distinction is ever to be in any sense psychologically " explained." To begin with, it is very questionable whether Hume was right in applying Locke's distinction of simple and complex to ideas in the narrower sense as well as to im- 1 The distinction between the thing and its properties, like all the foregoing distinctions, is one that might be more fully treated under the head of "Thought and Conception." Still, inasmuch as the material warrant for these concepts is contained more or less implicitly in our percepts, some consideration of it is in place here. 3 Treatise of Human Nature, book i. part i. 1. pressions. "That idea of red," says Hume, "which we form in the dark and that impression which strikes our eyes in the sunshine differ only in degree, not in nature." 3 But what he seems to overlook is that, whereas there can be a mere sensation red and such a presentation may for present purposes be regarded as simple we can only have an image or representation of a red thing or a red form, i.e., of red in some way ideally projected or intuited. In other words, there are no ideas answering to simple or isolated impressions : what are revived in memory and imagination are percepts, not unlocalized sensations and movements. It is not only that we cannot now directly observe such representations, because, for that matter, we can no longer directly observe even the original pre- sentations as merely elementary impressions; the point rather is that ideas as such are from the first complex, and do not begin to appear in consciousness apart from the impressions which they are said to reproduce till after these impressions have been frequently attended to together, and have been more or less firmly synthesized into percepts or intuitions. The effects of even the earliest of these syntheses or "associations " of impressions must of course in some way persist, or progress in perception would be impossible. On this account it has been usual to say that " perception " implies both " memory " and " imagina- tion" ; but such a statement can be allowed only so long as these terms are vaguely used. The dog's mouth waters only at the sight of food, but the gourmand's mouth will also water at the thought of it. We recognize the smell of violets as certainly as we recog- nize the colour when the spring brings them round again ; but few persons, if any, ca.i recall the scent when the flower has gone, so as to say with Shelley " Odours, when sweet violets sicken, Live within the sense they quicken " though most can recall the colour with tolerable clearness. In like manner everybody can perform innumerable complex voluntary movements which only a few can mentally rehearse or describe without the prompting of actual execution. And not only does such reproduction as suffices for perception fall short of that in- volved in reminiscence or memory in the narrower sense, but the manner in which the constituent elements in a perception are com- bined differs materially from what is strictly to be called the asso- ciation of ideas. To realize this difference we need only to observe first how the sight of a suit of polished armour, for example, instantly reinstates and steadily maintains all that we retain of former sensations of its hardness and smoothness and coldness, and then to observe how this same sight gradually calls up ideas now of tournaments, now of crusades, and so through all the changing imagery of romance. Though tlie percept is complex, it is but a single whole, and the act of perception is single too ; but, where, as is the case in memory and imagination, attention passes, whether voluntarily or non - voluntarily, from one repre- sentation to another, it is obvious that these several objects of attention are still distinct and tbat it is directed in turn to each. The term " association " seems only appropriate to the latter. To the connexion of the partial presentations in a complex, whether perception or idea, it would be better to apply the term " complica- tion," which was used in this sense by Herbart, and has been so used by many psychologists since. When we perceive an orange by sight we may say that its taste or feel is represented, when we perceive it by touch we may in like manner say that its colour is represented, symbolizing the whole complex in the first case sufficiently for our present purpose as Ctf, in the second as Fct. We might also symbolize the idea of an orange as seen by c'^/and the idea of an orange as felt by /' c t, using the accented letter to signify that different constituents are dominant in the two cases. What we have, then, to observe is briefly (1) that the processes by which the whole complex c'tforfct is brought into conscious- ness differ importantly from the process by which C or F rein- states and maintains tf or c t, and (2) that c, t, and/ never have that distinct existence as representations which they had as pre- sentations or impressions. The mental synthesis which has taken place in the evolu- tion of the percept can only partially fail in the idea, and never so far as to leave us with a chaotic " manifold " of mere sensational remnants. On the contrary, we find that in " constructive imagination " a new kind of effort is often requisite in order to dissociate these representational com- 3 Ibid. XX.
