103. The case then stands as follows. All that Locke says of body as the real thing-in-itself, and of its qualities as the essence of such thing, comes according to his own showing of an action of the mind which he reckons the source of fictions. ‘Body in itself’ is a substratum of ideas which the mind ‘accustoms itself to suppose.’ It perpetually recedes, as what was at first a substance becomes in turn a complex of qualities for which a more remote substratum has to be supposed--a ‘substance of body,’ a productive cause of matter. But the substance, however remote, is determined by the qualities to which it is correlative, as the cause by its effects; and every one of these--whether the most primary, solidity, or those which ‘the mind finds inseparable from every particle of matter,’ _i.e._ from the ‘solid parts of a body,’ [1]--as defined by Locke, is a relation such as the mind, ‘bringing one thing to and setting it by another’ (Book II. chap. xxv. sec. 1), can alone constitute. To Locke, however, overcome by the necessity of intelligence, as gradually developing itself in each of us, to regard the intelligible world as there before it is known, the real must be something which would be what it is if thought were not. Strictly taken, this must mean that it is that of which nothing can be said, and some expression must be found by means of which it may do double duty as at once apart from consciousness and in it. This is done by converting ‘the primary qualities of body, though obviously complex ideas of relation, into simple feelings of touch,’ [2] and supposing the subject of this sensation to be related to its object as wax to the seal. If we suppose this relation, again, which is really within the mind and constituted by it, to be one between the mind itself, as passive, and the real, we obtain a ‘real’ which exists apart from the mind, yet copies itself upon it. The mind, then, so far as it takes such a copy, becomes an ‘outer sense,’ as to which it may be conveniently forgotten that it is a mode of mind at all. Thus every modification of it, as an ‘actual present sensation,’ comes to be opposed to every idea of memory or imagination, as that which is not of the mind to that which is; though there is no assignable difference between one and the other, except an indefinite one in degree of vivacity, that is not derived from the action of the mind in referring the one to an object, constituted by itself, to which it does not refer the other. [1] Cf Book II. chap. viii. sec. 9. The primary qualities of body are ‘such as sense constantly finds in every particle of matter, which has bulk enough to be perceived, and the mind finds inseparable from every particle of matter, though less than to make itself singly be perceived by our senses.’