of one or both of the presentations. There is no “ unalterably fixed unit ” certainly, but, on the other hand, “the mutual relations of impressions ” are not everything. 15. The term “ field of consciousness ” has occurred sundry times in the course of this exposition: it is one of several em-Subcon- ployed in describing what have been incidentally “°"'"s"e“' referred to as “ degrees or grades of consciousness ” -a difficult and perplexing topic that we must now endeavour further to elucidate. Sailors steering by night are said to look at the pole-star, “ the cynosure of every eye, ” but this does not prevent them from seeing the rest of the starry vault. At a conversazione we may listen to some one speaker while still hearing the murmur of other voices, and while listening we may also see the speaker and thereby identify him the better. What in these instances is looked at or listened to has been called the “focus ” of consciousness, the rest of what is heard or seen or otherwise -presented being called the “ field ” within which attention is thus concentrated or brought to a point. Of these objects beyond the focus we have then only a lower degree of consciousness, and the more “distant ” they are from the centre of interest the fainter and obscurer they are supposed to be or to become. Now, it is obvious that the continuity here implied, if strictly taken, logically commits us to a field of consciousness extending with ever diminishing intensity ad indejnitum. But we have next to notice certain new 'features that have led psychologists to give to the term field of consciousness a more restricted meaning. A meteor flashing
across the sky would certainly divert the helmsman's attention, and for the nonce he would look at that and not at the star in the Little Bear's tail; a voice at our elbow accosting us, we should turn to the new speaker and listen to him, still hearing it may be, but no longer “ following, ” the discourse thus for us interrupted. In these cases a change in the field of consciousness brings about a non-voluntary change in the focus. But it only does so provided it is sufficiently intense and abrupt, and the more attention is already concentrated the less effective a given disturbance will be. A whole swarm of meteors might have streaked the sky unheeded while Ulysses, life in hand, steered between Scylla and Charybdis, just as all the din of the siege failed to distract Archimedes bent over his figures in the sand. On the other hand, we can voluntarily transfer the focus of consciousness to any object within the field, provided again this is sufficiently differentiated from the rest. But, more than that, we can not only of our own motion turn to lock at or to listen to what we have only seen or heard, but not noticed before; we can also look out or listen for something not as yet distinguishable, perhaps not as yet existing at all. And here again the concentration of attention may be maximal, as when a shipwrecked crew scan the horizon for a sail, or a beleaguered troop hearken for the oncoming of rescue. Now, such anticipated presentations as soon as they are clearly discernible have already a certain finite intensity, and so they are said to have passed over “ the threshold ”-to use Herbart's now classic phrase-and to have entered the field of consciousness. Afterwards 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 an ultraliminal or subliminal phrase where too it only changed continuously? The latter alternative constitutes the hypothesis of subconsciousness.
According to this hypothesis the total field with which ive began is divided into two parts by what Fechner emphatically called “the fact of the threshold, ” and the term field of consciousness is henceforth restricted to that part within which the focus of consciousness always lies, the outlying part being the region of subconsciousness. Difhculties now begin to be apparent. The intensity or vivacity of a presentation within the field of consciousness depends partly on what we may call its inherent or absolute intensity, partly on the attention that it receives; but this does not hold of presentations in subconsciousness. These sub-presentations, as we ought perhaps to call them, cannot be severally and selectively attended to, cannot be singled out as direct objects of experience. Many psychologists have accordingly maintained not only that they cannot with propriety be called presentations, but that they have no strictly psychical existence at all. This, however, is too extreme a view. If nothing of a presentational character can exist save in the field of consciousness as thus circumscribed by a definite boundary or threshold, a breach of continuity is implied such as we nowhere else experience: even the field of sight, from which the metaphor of a field of consciousness is derived has no such definite margin. The threshold then is not comparable to a mathematical line on opposite sides of which there is an intensive discontinuity. This has been amply proved by the psycho physical investigations of Fechner and others. We listen, say, to a certain sound as it steadily diminishes; at length we cease to hear it. Again, we listen for this same sound as it steadily increases and presently just barely hear it. In general it is found that its intensity in the former case is less than it is in the latter, and there is also in both cases a certain margin of doubt between clear presence and clear absence; the presentation seems to flicker in and out, now there and now gone. Further, in comparing differences in sensations-of weight, brightness, temperature, &c.-we may fail wholly to detect the difference between a and b, b and c, and yet the difference between a and c may be clearly perceived. We have thus to recognize the existence of a difference between sensations, although there is no so-called “sensation of difference.” But if this much continuity must be admitted we can hardly fail to admit more. If differences of presentation exist within the held of consciousness beyond the outermost verge of the threshold of difference, ” we cannot consistently deny the existence of any presentations at all beyond the threshold of consciousness. Since the field of consciousness varies greatly and often suddenly with the amount and distribution of attention, we must, as already said, either recognize such subconscious presentations or suppose that clearly differentiated presentations, presentations that is to say of Hnite intensity, pass abruptly into or out of existence with every such variation of the field.
The hypothesis of subconsciousness, then, is in the main nothing more than the application to the facts of presentation of the law of continuity, its introduction into psychology being due to Leibnitz, who first formulated that law. Half the difficulties in the way of its acceptance are due to our faulty terminology. With Leibnitz consciousness was not coextensive with all psychical life, but only with certain higher phases of it? Of late, however, the tendency has been to make consciousness cover all stages of mental development, and all grades of presentation, so that a presentation of which there is no consciousness resolves itself into the manifest contradiction of an unpresented presentation-a contradiction not involved in Leibnitz's “ unapperceived perception.” But such is not the meaning intended when it is said, for example, that a soldier in battle is often unconscious of his wounds or a scholar unconscious at any one time of most of the knowledge “ hidden in the obscure recesses of his mind.” There would be no point in saying a subject is not conscious of what is not presented at all; but to say that what is presented lacks the intensity requisite in the given distribution of attention to change that distribution appreciably is pertinent enough. Subconscious presentations may tell on conscious life-as sunshine or mist tells on a landscape, or the underlying writing on a palimpsest-although lacking either the intensity or the individual distinctness requisite to make them definite features. Even if there were no facts to warrant J
1 The following brief passage from his Principes de la nature et de la grace (§ 4) shows his meaning: “ Il est bon cle faire distinction entre la Perception, qui est l'état intérieur de la'Monade représentant les choses externes, et l'Apperception, qui est la Conscience, on la connaissance reflexive de cet état intérieur, laquelle n'est point donnée a toutes les ames, ni toujours <1 la méme éme. Et c'est faute de cette distinction que les Cartésiens ont manqué, en comptant pour rien les perceptions dont on ne s'apper§ oit pas, comme le peuple compt;=: pour rien les corps in sensibles ' (Op. Phil. Erdmann's ed., p. 715 .