"'When I looked toward the window it always seemed to me as if a shutter had been put up close before my eyes, and that upon this shutter a colorer had wiped off his brushes of different colors, white, blue, green, yellow, and red, all in motley confusion. Individual things, as I now see them, I could not, at that time, perceive and distinguish upon it; it was absolutely hideous to look upon.'"
By this, as well as by the experiences with persons born blind and afterward surgically treated, it is clearly demonstrated that colors and degrees of brightness are severally apprehended before forms and distances can be perceived. The case must be the same with the normal human child in the first weeks after birth.
After discrimination of the luminous sensations, the boundary-lines of bright plane surfaces are next clearly discerned; then come forms, and, last of all, the distances of these.
With reference to this progress of the normal infant in learning to see, the accounts of persons born blind and afterward surgically treated are again of great value. After the famous question put by Molyneux to Locke, whether an intelligent person, blind from birth, would be able immediately after an operation to distinguish a sphere from a cube by means of the eye alone, had been answered in the negative, the opinion was accepted as satisfactory that such a person learns the distinction only by means of the sense of touch. Thus, the perception of difference would come later, after the sight of different forms, only by means of the tactual memory.
In truth, however, very many forms are discerned as different purely by means of the eye, without the possibility of aid from any other sense. Phenomena exclusively optical, which, like the rainbow, can not be apprehended by touch or by hearing, are distinctly perceived by the child at a very early period. Without touching, the different forms of objects would be perceived by means of sight alone, and that even by a child unable to touch, through movements of the eyes and head, changes of bodily position, of attitude and posture, and through practice in accommodation and in the observation of differences of brightness.
The fact correctly predicted by Molyneux, that those born blind but afterward surgically treated can not, by means of the eye alone, distinguish the form of a sphere from that of a cube, must accordingly be supplemented to this extent, viz., that such persons are capable, just as are normal children who can see, of learning this difference of form by means of the eye alone without the direct intervention of the sense of touch; for the co-ordination of the retinal excitations in space and time by means of the intellect, quite independently of all impressions from other departments of sense, is possible, and is in countless cases actual, just as is the learning of differences of form solely by means of the sense of touch in children who are born blind and never learn to see.