Fig. 65 (after Weber).
The dotted lines give the real course of the points, the continuous lines the course as felt.
Now my first thesis is that this extensity, discernible in each and every sensation, though more developed in some than in others, IS THE ORIGINAL SENSATION OF SPACE, out of which all the exact knowledge about space that we afterwards come to have is woven by processes of discrimination, association, and selection.
The Construction of Real Space.—To the babe who first opens his senses upon the world, though the experience is one of vastness or extensity, it is of an extensity within which no definite divisions, directions, sizes, or distances are yet marked out. Potentially, the room in which the child is born is subdivisible into a multitude of parts, fixed or movable, which at any given moment of time have definite relations to each other and to his person. Potentially, too, this room taken as a whole can be prolonged in various directions by the addition to it of those farther-lying spaces which constitute the outer world. But actually the further spaces are unfelt, and the subdivisions are undiscriminated, by the babe; the chief part of whose education during his first year of life consists in his becoming acquainted with them and recognizing and identifying them in detail. This process may be called that of the construction of real space, as a newly apprehended object, out of the original chaotic experiences of vastness. It consists of several subordinate processes:
First, the total object of vision or of feeling at any time must have smaller objects definitely discriminated within it;
Secondly, objects seen or tasted must be identified with objects felt, heard, etc., and vice versa, so that the same 'thing' may come to be recognized, although apprehended in such widely differing ways;
Third, the total extent felt at any time must be conceived as definitely located in the midst of the surrounding extents of which the world consists;
Fourth, these objects must appear arranged in definite order in the so-called three dimensions; and
Fifth, their relative sizes must be perceived—in other words, they must be measured.
Let us take these processes in regular order.