That Mill’s reasoning should have satisfied himself and his immediate disciples is strange. But that the wider public of thinking men, whom he so powerfully influenced, should on the strength of this flimsy philosophy adopt an attitude of dogmatic assurance both as to what can be known and what cannot, is surely stranger still. Thus, at least, I thought nearly half a century ago, and thus I think still. Consider, for example, a typical form of the ordinary agnostic position: that presented by Leslie Stephen. The best work of this excellent writer was biographical and literary; but he was always deeply interested in speculation; and his own creed seems early to have taken its final shape under the philosophical influences of the British empiricists. He regarded the “appeal to experience” as the fundamental dogma of agnosticism, and by the “appeal to experience” he meant what Mill meant by it. He sincerely supposed that this gave you indisputable knowledge of “phenomena,” and that if you went beyond “phenomena” you were dreaming, or you were inventing. This is a possible creed; and it is, in fact, the creed held implicitly, or explicitly, by many thousands of quite sensible people. But why should those who hold it suppose that it must always satisfy impartial inquirers? Why should they assume that those who reject it are sacrificing their reason to their prejudices or their fancies? It may represent the best we can do, but is it, after all, so obviously reasonable? On this subject the empirical agnostic has no doubts. He holds, with unshaken confidence, that nothing deserves to be believed but that which in the last resort is proved by “experience”; that the strength of our beliefs should be exactly proportioned to the evidence which “experience” can supply, and that every one knows or can discover exactly what this evidence amounts to. Leslie Stephen refers to a well-known aphorism of Locke, who declared that “there is one unerring mark by which a man may know whether he is a lover of truth in earnest, viz. the not entertaining any proposition with greater assurance than the proofs it is built on will warrant.” Upon which Leslie Stephen observes that the sentiment is a platitude, but, in view of the weakness of human nature, a useful platitude. Is it a platitude? Did Locke act up to it? Did Hume act up to it, or any other of Leslie Stephen’s philosophic progenitors? Does anybody act up to it? Does anybody sincerely try to act up to it? Read through the relevant chapters in Locke’s Essay, and observe his ineffectual struggles, self-imprisoned in the circle of his own sensations and ideas, to reach the external world in which he believed with a far “greater assurance” than was warranted by any proofs which _he_, at all events, was able to supply. Read Hume’s criticism of our grounds for believing in a real world without, or a real self within, and compare it with his admission that scepticism on these subjects is a practical impossibility.