But precisely because of its importance, the attempt to determine a theory of knowledge should be thorough-going, or it should not be made at all. Such an attempt is essentially an appeal from common sense to philosophy, from unreasoned certainty to reasoned certainty. Being such, it is manifestly illogical to permit common sense to have anything to do with the matter. Common sense is either capable of giving us a philosophy, or it is not; if it is, the history of philosophy is nothing but a record of stupendous blunders and misdirected energies; if it is not, any philosophy which is based upon it rests on the evidence of an incompetent witness. Nor can such a philosophy defend itself by contending that it is only a refined common sense, so to speak,—a philosophical common sense to which it appeals. If the common sense of the plain man cannot be trusted to give us a philosophy, how can we trust the common sense of Reid and Hamilton? Precisely in so far as a philosophy rests on common sense, it is unreasoned; but philosophy originated, as we have seen, from the mind's reluctance to acquiesce in unreasoned principles.
These remarks are made, not so much for the purpose of criticising the common sense philosophy, as in order to indicate the method that I shall try to follow in the investigation of this subject. Propositions that are reported to be true or probable, merely on the testimony of common sense, however emphatic, I shall aim to disregard. Hypotheses against which nothing can be said, except that they are absurd, when their absurdity consists in their being at variance with the principles of common sense, I shall consider myself entitled to make.
I can most conveniently state my answer to two of the questions which a Theory of Knowledge undertakes to answer, by pointing out how far I agree with Bain. He says that the belief in memory is a primary assumption.[1] "Unless we trust our recollection, our knowledge is limited to what is now present, and we cannot compare two successive experiences, or declare two facts to succeed one another. We have one moment the consciousness of thirst; the next moment we have
- ↑ Logic, new and revised ed., p. 670.
