§ 2. Our declaration that the principle of the self-consistency of the real affords a certain and infallible criterion of reality, may probably provoke a sceptical doubt which is of such importance that we must give it full consideration before making any further advance. I state the difficulty in what appears to me its most reasonable and telling form. “Your alleged criterion,” it will be said, “is simply the logical Law of Contradiction expressed in a novel and misleading way. Now, the Law of Contradiction, like all purely logical laws, is concerned not with real things, but exclusively with the concepts by which we think of them. When the logician lays it down as a fundamental truth of his science that _A cannot be both B and not B_, his A and B stand not for things “in the real world to which our thoughts have reference,” but for concepts which we frame about the things. His law is thus purely what he calls it, a Law of Thought; he says, and says truly, “you cannot, at the same time, and in the same sense, _think_ both that A is B, and that it is not B”; as to whether such a state of things, though unthinkable to us, may be real “as a fact,” he makes no assertion. You take this law of our thinking, silently assume that it is also a law of the things about which we think, and go on to set it up as an infallible criterion of their reality. Your procedure is thus illegitimate, and your pretended criterion a thing of nought.”[12] Our reply to this common sceptical objection will incidentally throw an interesting light on what was said in the last chapter of the close connection between the problems of Logic and those of Metaphysics. In the first place, we may at least meet the sceptic with an effective _tu quoque_. It is you yourself, we may say, who are most open to the charge of illegitimate assumption. Your whole contention rests upon the assumption, for which you offer no justification, that because the Law of Contradiction is admittedly a law of thought, it is therefore _only_ a law of thought; if you wish us to accept such a momentous conclusion, you ought at least to offer us something in the nature of a reason for it. Nor shall we stop here; we shall go on to argue that the sceptic’s interpretation of the Law of Contradiction rests on a positive confusion. By a Law of Thought may be meant either (_a_) a _psychological_ law, a true general statement as to the way in which we actually do think, or (_b_) a _logical_ law, a true general statement as to the conditions under which our thinking is valid; the plausibility of the sceptical argument arises from an unconscious confusion between these two very different senses of the term. Now, in the first place, it seems doubtful whether the principle of contradiction is even true, if it is put forward as a psychological law. It would be, at least, very hard to say whether a human being is capable or not of holding at once and with equal conviction the truth of two contradictory propositions.