PSYCHOLOGY 47 continuum implies. This persistence is best spoken of as retentiveness ; it is sometimes confounded with memory, though this is something much more complex and special. Retentiveness is both a biological and a psychological fact; memory is exclusively the latter. In memory there is necessarily some contrast of past and present, in re- tentiveness nothing but the persistence of the old. If psychologists have erred in regarding the presentations in consciousness together as a plurality of units, they have erred in like manner concerning the persisting residua of such presentations. As we see a certain colour or a cer- tain object again and again, we do not go on accumulating images or representations of it, which are somewhere crowded together like shades on the banks of the Styx ; nor is such colour, or whatever it be, the same at the hundredth time of presentation as at the first, as the hundredth impression of a seal on wax would be. There is no such constancy or uniformity in mind. Obvious as this must appear when we pause to think of it, yet the explanations of perception most in vogue seem wholly to ignore it. Such explanations are far too mechanical and, so to say, atomistic; but we must fall back upon the unity and continuity of our presentation-continuum if we are to get a better. Suppose that in the course of a few minutes we take half a dozen glances at a strange and curious flower. We have not as many complex presenta- tions which we might symbolize as F lt F 2 , F 3 . But rather, at first only the general outline is noted, next the disposi- tion of petals, stamens, &c., then the attachment of the anthers, form of the ovary, and so on ; that is to say, symbolizing the whole flower as [p 1 (a b) s' (c d) o' (f g} we first apprehend say [p . . / . . o'], then [p (a b) s' . . o'.j, or [/>' (a . .) s (c . .) o' (/ . .)], and so forth. It is because the earlier apprehensions persist that the later are an advance upon them and an addition to them. There is nothing in this process properly answering to the repro- duction and association of ideas : in the last and complete apprehension as much as in the first vague and inchoate one the flower is there as a primary presentation. There is a limit, of course, to such a procedure, but the instance taken, we may safely say, is not such as to exceed the bounds of a simultaneous field of consciousness. Now the question is : Ought we not to assume that such increase of differentiation through the persistence of preceding differentiations holds of the contents of consciousness as a whole? Here, again, we shall find limitations, limitations too of great practical importance ; for, if presentations did not pale as well as persist, and if the simpler presentations admitted of indefinite differentiation, mental advance unless the field of consciousness, i.e., the number of pre- sentations to which we could attend together, increased without limit would be impossible. But, allowing all this, it is still probably the more correct and fundamental view to suppose that, in those circumstances in which we now have a sensation of, say, red or sweet, there was in the primitive consciousness nothing but a vague modification, which persisted ; and that on a repetition of the circum- stances this persisting modification was again further modified. The whole field of consciousness would thus, like a continually growing picture, increase indefinitely in complexity of pattern, the earlier presentations not disap- pearing, like the waves of yesterday in the calm of to-day, but rather lasting on, like old scars that show beneath new ones. There is yet one more topic of a general kind calling for attention before we turn to the consideration of parti- cular presentations the hypothesis of unconscious mental modifications, as it has been unfortunately termed, the hypothesis of subconsciousness, as we may style it to avoid this contradiction in terms. It is a fact easily verified, that we do not distinguish or attend separately to presentations of less than a certain assignable intensity. On attaining this intensity presentations are said to pass over the threshold of consciousness, to use Herbart's now classic phrase. What are we to say of them before they have attained it 1 After they have attained it, any further increase in their intensity is certainly gradual ; are we then to suppose that before this their intensity changed instantly from zero to a finite quantity, and not rather that there was also a subliminal stage where too it only changed continuously ? The latter alternative constitutes the hypothesis of subconsciousness. According to this hypothesis, a presentation does not cease to be so long as it has any intensity, no matter how little. We can directly observe that an increase in the intensity of many complex presentations brings to light details and differences before imperceptible ; since these details are themselves presenta- tions, they have been brought by this increase from the subconscious stage into the field of consciousness. Simi- larly, presentations not separately distinguishable, because of too close a proximity in time, become distinguishable when the interval between them is such as to allow of a separate concentration of attention upon each. Again, we find that presentations "revived" or re-presented after their disappearance from the field of consciousness appear fainter and less distinct the longer the time that has elapsed between their exits and their re-entrances. Nobody hesi- tates to regard such obliviscence as a psychological fact ; why, then, should we hesitate to suppose that presenta- tions, even when no longer intense enough directly to influence attention, continue to be presented, though with ever lessening intensity 1 On the whole we seem justified in assuming three grades of consciousness thus widely understood (1) a centre or focus of consciousness within (2) a wider field, any part of which may at once become the focus. Just as in sight, surrounding the limited area of distinct vision on which the visual axes are directed, there is a wider region of indirect vision to any part of which those axes may be turned either voluntarily or by a reflex set up by the part itself, as happens, e.g., with moving objects quite on the margin of vision. But in describing (3) subconscious- ness as the third grade, this simile, due to Wundt, more or less forsakes us. Presentations in subconsciousness have not the power to divert attention, nor can we voluntarily concentrate attention upon them. Before either can happen the subconscious presentations must cross the threshold of consciousness, and so cease to be subconscious ; and this, of course, is far from being always possible. Now in the case of sight an object may fail to catch the eye, either because, though within the field of sight, it is too far away to make a distinct impression or because it is outside the field altogether. But we cannot conveniently interpret " threshold of consciousness " in keeping with the latter alternative ; mere accretion from without is a conception as alien to psychology as it is to biology. We must make the best we can of a totum objectivum differen- tiated within itself, and so are confined to the first alternative. Our threshold must be compared to the sur- face of a lake and subconsciousness to the depths beneath it, and all the current terminology of presentations rising and sinking implies this or some similar figure. This hypothesis of subconsciousness has been strangely mis- understood, and it would be hard to say at whose hands it has suffered most, those of its exponents or those of its opponents. In the main it is nothing more than the application to the facts of presentation of the law of continuity, its introduction into psycho- logy being due to Leibnitz, who first formulated that law. Half the difficulties in the way of its acceptance are due to the manifold ambiguities of the word consciousness. With Leibnitz consciousness was not coextensive with all psychical life, but only with certain
