out the hand, lifting, etc., are carried out. Persistence is thus known through a uniform or unchanging relation (or sum of relations), viz., the occurrence of a certain group of experiences of contact and resistance on carrying out a particular group of

movements.

Of great importance in connexion with the development of this apprehension of persistent object is the experience the child obtains in connexion with his own body. The persistence of the several parts of this object when no longer touched discloses itself through the persistence of the sensations connected with, and localised in, these parts. It is probable, as we have seen, that a child fashions other objects on the model of his own body, endowing them with sensations analogous to his own; and if this is so, we can understand the more readily how he comes to attribute persistence or continuous existence to these objects.1

The full knowledge of unity and persistence of object presupposes the experience of the movement of ourselves and of objects, and the attendant changes of position. The cluster of qualities composing an object only becomes clearly discriminated from other clusters by movement. Thus the spoon becomes isolated as a single object when it is found that it yields the same group of experiences whatever its local relations to the cup and other objects. The same experience of movement and change of position would extend the idea of persistence by showing that objects continue to exist somewhere after changing their position. It is highly probable that, to the infant mind, the disappearance of an object is tantamount to its destruction. It is only a wider experience, familiarising it with changes of locality, which enables it to reach the idea of persistence, or identity of object as we understand it.

Such a tactual intuition as that described would supply a sufficient means of distinguishing and recognising objects apart from sight. Thus a blind child, by the complex of experiences gained on touching an orange, is able to recognise the object as an orange, thus. reinstating by means of active touch other sense-experiences, as those of smell and taste.

1 It is pointed out by Uphues (Wahrnehmung und Empfindung, p. 282 ff.) that the cognition of object as persistent is rather representative than presentative. Our immediate presentative apprehension of things is, strictly speaking, momentary.

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This tactual intuition involving a complex group of sensations would be a highly presentative mode of perception. We have now to pass to a mode of perception where the representative element is much more preponderant over the presentative than in the case of tactual perception.

§ 11a. Tactual Apprehension of Real Object. The perception of object is thus seen to be not merely the result of a (passive) process of integration or association, but to involve a certain element of constructive activity and of inference. A child acquires the idea of real objects persisting when no longer acting on his senses very gradually, and by a certain exercise of imagination and of reason. That is to say, using the analogies supplied by his experience, and more particularly what he knows of his own body, he frames a supposition by help of which he can render consistent and explain what his senses tell him.1

The complete apprehension of object involves, in addition to the cognition of material reality, unity, and persistence dealt with above, that of the relation of substance and attribute and of externality or the relation of the not-self to the self. The clear apprehension of these relations comes later. Thus the distinction between substance and attribute only arises after a measure of abstraction. To a child a thing is one indivisible whole, and remains such till analysis (abstraction) begins to resolve it into a number of qualities. This is seen in the fact that children name objects as wholes some time before they begin to qualify them, by calling them hard, and so forth. The fundamental fact in the distinction of substance and quality has already been touched on. It is the resisting aspect of a thing, its material quality as obstructing movement, which constitutes the essential element in its substantiality. The impressiveness and practical importance of this aspect, supplemented by the teaching of experience that it is the ever-present or constant factor, lead all of us to separate it out as par excellence the thing or substance, whereas the other and secondary qualities are recognised as of subordinate importance and as dependent on this.

With respect to the relation of the material object to the self, it is to be observed that this idea becomes distinct only when the consciousness of self has reached a certain development, which, as we shall see, first takes place after the inner representative life of imagination and thought has been developed, and the difference between sensation and idea, presentation and representation, clearly apprehended. At the same time, as we have seen, the ground of a vague apprehension of the relation is supplied in the simplest perception of real object. For the resisting object is known to the child through its opposition to his own movement, and on that very account is endowed with force analogous to that of which he begins to be aware in himself. And here it is evident the germ of the distinction between self and not-self emerges.3

1 This is well brought out by Lipps, Grundthatsachen des Seelenlebens, kap. xvii.; cf. G. F. Stout, Mind, xv. p. 26 ff.

2 On the whole question of the perception of object, see Bain, The Senses and the Intellect, p. 375 ff.; J. S. Mill, Examination of Sir W. Hamilton's Philosophy, chap. xiii.; Taine, On Intelligence, pt. ii. bk. ii. chap. i.; Ward, article, "Psychology," p. 55 f.; and Julius Pikler, The Psychology of Belief in Objective Existence (part i.).

(B) VISUAL PERCEPTION.

§ 12. Tactual and Visual Perception. While, as we have just seen, tactual perception is the most direct mode of apprehending things, it is limited in its range at any one moment. Our imaginary blind child would be able to perceive directly at any one time only a small portion of the external world, namely those objects which were within his reach and capable of being simultaneously touched.

Visual perception stands in marked contrast to this direct but limited mode of apprehension. In normal circumstances seeing is, as has been remarked, the customary mode of perception. It greatly transcends touching in the range of its grasp of external things. Thus in vision we apprehend objects not only near us, but at vast distances from us, such as the heavenly bodies. Again, by sight we are capable of apprehending in a single moment a wide field of objects in different directions and at different distances from us, that is to say, a whole region of the external world.

The predominance of visual perception is illustrated by a number of facts. In smelling, tasting, or touching an object which we do not see, the corresponding visual presentation (visual form with colour more or less distinct) is instantly recalled. Similarly a word always suggests to our mind first of all, and most irre. sistibly, the visual appearance of a thing. And this holds good with respect to objects which are of most interest to us in relation to other senses. Thus the word 'bell' calls up the bell-form before the bell-sound, the word 'orange,' the particular form and colour of the fruit before its taste.

The resources of sight, more particulurly the capability of the retina of receiving a multitude of finely differentiated local sensations, and the delicate movements of the eyes, enable this sense to develop a highly-complex mode of perception of its

A clear understanding of the true function of sight as a means of perception will, however, compel us to adopt the idea first clearly set forth by Berkeley, that in seeing objects in space the sense of sight is greatly aided by that of touch. We apprehend so much through sight because it gathers up and preserves for us under a representative or symbolic form experiences of active touch.

We will first trace out the development of an independent Visual Perception. After this we may study that more com

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plex mode of perception which arises through the associative integration of experiences of Touch and Sight.

§ 13. Visual Perception of Space. Here, as in the case of touch, we set out with the appreciation of extensive magnitude and plurality of sensations. Our visual idea of space, position of objects, and so forth, is obtained by help of this retinal discrimination. At the same time, this primordial distinctness of sensation answering to different retinal points only takes on a definitely spatial or local significance by the addition of movement.

In order, then, to understand the development of the visual perception of space, we may proceed, as in the case of tactual perception, to enquire into the nature and results of the experiences immediately connected with movements of the eyes. And for the sake of simplifying the problem we will suppose that a child has but one eye, and that this eye has but one sensitive retinal point, the yellow spot or area of perfect vision.

(a) Ocular Movement as Factor in Space-consciousness. The eye is capable of rotating in various directions, as to the right, upwards, and so forth, all such movements being resolvable into rotations about three axes, viz., a vertical axis, the horizontal optic axis,' and a third horizontal axis drawn through the centres of the two eye-balls. These movements which are executed by means of a system of six muscles,1 serve to bring the yellow spot opposite to different points of the field. This is commonly described as turning or directing the axis of vision (optic axis) from one point to another. In performing any particular movement our imaginary child would experience a series of sensations analogous to those experienced in carrying the finger-tips from point to point of space. Thus in moving the axis from a point A in the field of vision to a point B to the right of it he would experience a series of sensations of movement of a definite character. Here, too, the final sensation, answering to the position of the eye at the close of the movement, supplemented by the representation of the preceding members of the series, would supply materials for a rudimentary perception of movement of a particular direction and range.

1 On the nature and laws of ocular movement, see Wundt, op. cit., ii. p. 94 ff.; cf. Ladd, op. cit., p. 428 ff.

By repeating the series, by varying its rapidity, by reversing it, and finally by carrying out a variety of such pairs of movements in different directions, the perception of movement in a definite region of space would acquire a measure of distinctness, as in the case of manual movement.

In this way the child might explore the field of vision or map out the several positions of points on a surface, or in space of two dimensions. In a similar manner he could pass the optic axis over the surface of a body in different directions, and so obtain, by means of numerous series of muscular sensations with the concomitant trains of retinal sensations, a perception of its extension and the form and magnitude of the surface. Thus he might pass his eye from the centre of a circular body, as a wheel, to various points of the circumference. These movements might be supplemented by others along the contour (the circumference).

(b) Simultaneous Retinal Perception. Let us now suppose the child's eye to be supplied with its extended retinal surface, and its innumerable nerve-elements, together with the correlated extensity and plurality of sensations. The movements just described would now serve, as in the case of touch, to develop this primordial discrimination into a true appreciation of locality or position in space.

It is evident that, being thus endowed with a retina, our little explorer in carrying the axis of its eye from one part of the field to another would not instantly lose sight of a point as soon as his eye passed on to another, but would continue to see it in what is called indirect vision. Thus, in moving from the centre to a point on the circumference of the wheel, the retinal image of the former point would slide over a succession of retinal points. That is to say, the child would continue to receive the impression of this point (with decreasing degrees of distinctness), varied, however, by a succession of distinct accompaniments in the shape of the original differences of sensation corresponding to distinct retinal points. In like manner, the point of the circumference towards which he was moving would be seen 'indirectly' (with increasing degrees of distinctness) before the eye was fixed on it in 'direct' vision.

This conjoined experience of ocular movement and of varying (retinal) impression would lead to the ordering of visual

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