=188.= This doctrine of Bradley and Bosanquet is the converse of the epistemological doctrine I have to advocate. Owing to the continuity and relativity of space and time, they say, we are able to construct a systematic world, by judgment and inference, out of that fragmentary and yet necessarily complex existence which is given in sense-perception. My contention is, conversely, that since all knowledge is necessarily derived by an extension of the _This_ of sense-perception, and since such extension is only possible if the _This_ has that fragmentary and yet complex character conferred by a form of externality, therefore some form of externality, given with the _This_, is essential to all knowledge, and is thus logically _à priori_. Bradley's argument, if sound, already proves this contention; for while, on the one hand, he uses no properties of space and time but those which belong to every form of externality, he proves, on the other hand, that judgment and inference require the _This_ to be neither single nor self-subsistent. But I will endeavour, since the point is of fundamental importance, to reproduce the proof, in a form more suited than Bradley's to the epistemological question. =189.= The essence of my contention is that, if experience is to be possible, every sensational _This_ must, when attended to, be found, on the one hand, resolvable into _Thises_, and on the other hand dependent, for some of its adjectives, on external reference. The second of these theses follows from the first, for if we take one of the _Thises_ contained in the first _This_, we get a new _This_ necessarily related to the other _Thises_ which make up the original _This_. I may, therefore, confine myself to the first proposition, which affirms that the object of perception must contain a diversity, not only of conceptual content, but of existence, and that this can only be known if sense-perception contains, as an element, some form of externality. My premiss, in this argument, is that all knowledge involves a recognition of diversity in relation, or, if we prefer it, of identity in difference. This premiss I accept from Logic, as resulting from the analysis of judgment and inference. To prove such a premiss, would require a treatise on Logic; I must refer the reader, therefore, to the works of Bradley and Bosanquet on the subject. It follows at once, from my premiss, that knowledge would be impossible, unless the object of attention could be complex, _i.e._ not a _mere_ particular. Now could the mental object--_i.e._, in this connection, the object of a cognition--be complex, if the object of immediate perception were always simple?