ABSTRACT
We have now given what account we could of the structure of knowledge in its higher and lower forms. We have shown that it rests upon a certain limited number of presuppositions, some of which, called collectively the inductive principles, have been stated as universal truths holding of reality at large, while others, such as memory or construction, may be looked on as powers or faculties of the mind which forms and possesses knowledge, and are for our inquiry ultimate facts, since any attempt to explain their origin or character postulates at the outset their general trustworthiness. In the progress of our inquiry we have had at several points to distinguish between truth and falsity, and between valid or invalid methods of forming assertions. And we have so far assumed, without hesitation or self-criticism, that every assertion which issues from one or several of these presuppositions, and from no others, is valid, and is to be taken as true. But now that our survey is complete, a deeper question naturally suggests itself. Having admitted the possibility of error, it may be asked, Why, after all, should we take these half-dozen methods (as we may call them generically) of forming our assertions as especially valid? We have used them, one and all, for testing various judgments; but what shall test them? Or have they an inherent right to stand untested? If we are not to leave this question unanswered, we must get some notion of what validity means, and what sort of test can be assigned for it compatibly with the limits of the human intellect.
