=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. 1) =Subdivision or Discrimination.=--Concerning this there is not much to be added to what was set forth in Chapter XIV. Moving parts, sharp parts, brightly colored parts of the total field of perception 'catch the attention' and are then discerned as special objects surrounded by the remainder of the field of view or touch. That when such objects are discerned apart they should appear as thus surrounded, must be set down as an ultimate fact of our sensibility of which no farther account can be given. Later, as one partial object of this sort after another has become familiar and identifiable, the attention can be caught by more than one at once. We then see or feel a number of distinct objects alongside of each other in the general extended field. The 'alongsideness' is in the first instance vague--it may not carry with it the sense of definite directions or distances--and it too must be regarded as an ultimate fact of our sensibility.