immediately aware of; and it arises, we may suppose, from the limitation of the mind, from its inability to comprehend totality, to seize the whole of being as such, in its entirety. Thus, in consequence of our definition of extension (par. 9), we may say that nature, the external world, possesses for the mind, extension; whether we say that this extension is discovered in nature, or imposed upon nature by the mind, will depend upon our philosophic views or preconceptions.
From the effort of the mind to apprehend something outside itself we must infer that the awareness of something which is not mind, the awareness, that is, that the mind itself is not the whole of reality, but only a part of it, constitutes a fundamental characteristic of its being; it is in this internal evidence that we have to look for proof that it is not commensurate with the universe, which fact will then account for its inability to comprehend the totality of being as a single whole (if we are justified in supposing that, in order to comprehend the whole universe at once, the mind would have to be commensurate with it), and for the necessity of dividing this totality into fractions which it can comprehend.
21. Since we discover extension in the whole of our perceptual data, it follows that of parts of the world as such we can predicate everything which we can predicate of an entity having extension, i.e., inclusiveness, exclusiveness, and intersection of its various parts, and that we can postulate in them the existence of elementary parts, i.e., parts which have no extension as regards any attribute by virtue of which they are parts of our perceptual data. A satisfactory definition of such an elementary part will be attempted in a later paragraph.
The relations which are deducible from the fundamental relation of extension do not, however, exhaust the logical relations which the mind discovers in (or imports into) the totality of its perceptions. Of the parts of our perceptual data which can be called separate, it is hardly possible, on the basis of the relation of extension, to say more than that they have no common part; but for that very reason we cannot usefully apply this relation to the elements of our experience, to relations of which we endeavour to reduce phenomena. The problem is made easier by the fact that the mind discovers in (or imports into) its perceptual data a second fundamental relation, namely that of order, i.e., we can arrange individual parts or components of our perceptual data in series according to many different characteristics of given perceptions.
