produced is sufficient or not?[13] Thus we see that the paradox of Mr. Bradley, that rational doubt itself logically implies infallibility in respect of some part of our knowledge, is no more than the simple truth. We see also that the doubt whether the ultimate presuppositions of valid thinking may not be merely “relatively” valid, has no meaning. If the sceptic’s doubt whether Reality is ultimately the self-consistent system that it must be if any of our thinking can be true is to lay any claim to rationality, it must take the form of the assertion, “I positively know something about the nature of Reality which makes it reasonable to think that Reality is incoherent,” or “Self-consistency is inconsistent with what I positively know of the nature of Reality.” Thus the sceptic is forced, not merely to lay claim to absolute and certain knowledge, but to use the test of consistency itself for the purpose of disproving or questioning its own validity. Our criterion of Reality, then, has been proved infallible by the surest of methods; we have shown that its truth has to be assumed in the very process of calling it in question. § 4. Reality, then, in spite of the sceptic’s objections, is truly known to be a connected and self-consistent, or internally coherent, system; can we with equal confidence say anything of the data of which the system is composed? Reflection should convince us that we can at least say as much as this: all the materials or data of reality consist of _experience_, experience being provisionally taken to mean psychical matter of fact, what is given in immediate feeling. In other words, whatever forms part of presentation, will, or emotion, must in some sense and to some degree possess reality and be a part of the material of which reality, as a systematic whole, is composed; whatever does not include, as part of its nature, this indissoluble relation to immediate feeling, and therefore does not enter into the presentation, will, and emotion of which psychical life is composed, is not real. The real is experience, and nothing but experience, and experience consists of “psychical matter of fact.”[14]