A more recent version of the same doctrine, which avoids the old associationist mistake of treating perception as a merely passive reception of a given material, is that the unity of the one subject of many predicates is ultimately derived from the unity of our own acts of attention. The qualities appear to belong to “one” thing because _we_ attend to them together as one in a single moment of attention. Thus the unity of substance which common sense believes itself to find in its objects has really been put into them by the perceiving mind itself. What is “given” to it is a disconnected plurality of qualities; by attending to groups of them as one it makes those groups into the attributes of a single reality. This is the essence of the doctrine of Kant, according to which the concept of “substance” is simply one form of the “synthetic unity of apperception” _i.e._ the process by which we project the unity of our own acts of attention into their objects, and thus create an orderly world for our own thought out of sensations which as they are given to us are a chaos. In principle, Kant’s doctrine, though intended as a refutation of Hume’s Associationism, only differs from Hume’s in the stress it rightly lays on the element of subjective interest in perception; the two theories agree on the main point, that the bond which unites the many qualities of sense perception into one thing is a subjective one,—in Hume’s expressive phrase, a “fiction of the mind.”[81] With the psychological aspects of this doctrine we are not directly concerned in the present inquiry. For us the problem is not by what precise steps the mind comes to “feign” a unity in its objects which is not really there, but whether this conception of a feigned or subjective unity imposed by the mind upon a number of actually disconnected qualities is itself ultimately intelligible. Thus the metaphysical issue may be narrowed down to the following question: Can we intelligibly hold that a thing is in reality simply a number of qualities, not in their own nature connected, which we arbitrarily regard for our own purposes as one?[82] In other words, can we say the thing is simply identical with its qualities considered as a mere sum or collection, and any further unity of the kind the old Metaphysics denotes by “substance” a mental addition of our own to the facts?