Let us assume for the moment that the real difficulty with Mr. Bosanquet's conception, the error that keeps him traveling in his hopeless circles, is the notion that truth is a matter of reference of ideas as such to reality as such, leading us to oscillate between the alternatives that either all ideas have such reference, and so are true, constitute knowledge; or else none have such reference, and so are false; or else are mere ideas to which neither truth nor falsity can be attributed. Let us ask if truth is not rather some _specific_ relation within experience, something which characterizes one idea rather than another, so that our problem is not how an idea can refer to a reality beyond itself, but what are the marks by which we discriminate a true reference from a false one. Then let us ask for the criterion used in daily life and in science by which to test reality. If we ask the philosophically unsophisticated individual why he believes that his house still exists when he is away from it and has no immediate evidence of the fact, he will tell you it is because he has found that he can go back to it time and again and see it and walk into it. It never fails him when he acts upon the assumption that it is there. He would never tell you that he believed in its existence when he was not experiencing it because his mental picture of his house stood for and represented accurately an object in the real world which was nevertheless of a different order of existence from his mental picture. When you ask the physicist why he believes that the laws of motion are true, he will tell you that it is because he finds that bodies always do behave according to them. He can predict just what a body will do under given circumstances. He is never disappointed however long he takes it for granted that the laws of motion are true and that bodies behave according to them. The only thing that could make him question their truth would be to find some body which did not prove to behave in accordance with them. The criterion is the same in both cases. It is the practical criterion of what as a matter of fact will work. That which can safely be taken for granted as a basis for further action is regarded as real and true. It remains real so long, and only so long, as it continues to fulfil this condition. As soon as it ceases to do so, it ceases to be regarded as real. When a man finds that he can no longer obtain the accustomed experience of seeing and entering his house, he ceases to regard it as real. It has burned down, or been pulled down. When a physicist finds that a body does not, as a matter of fact, behave as a given law leads him to expect it would behave, he ceases to regard the law as _true_.