A like remark applies to David Hume, of whose philosophy the central principle is the denial of the relation of cause and effect. He would deprive men of a familiar term which they can ill afford to lose; but he seems not to have observed that this alteration is merely verbal and does not in any degree affect the nature of things. Still less did he remark that he was arguing from the necessary imperfection of language against the most certain facts. And here, again, we may find a parallel with the ancients. He goes beyond facts in his scepticism, as they did in their idealism. Like the ancient Sophists, he relegates the more important principles of ethics to custom and probability. But crude and unmeaning as this philosophy is, it exercised a great influence on his successors, not unlike that which Locke exercised upon Berkeley and Berkeley upon Hume himself. All three were both sceptical and ideal in almost equal degrees. Neither they nor their predecessors had any true conception of language or of the history of philosophy. Hume's paradox has been forgotten by the world, and did not any more than the scepticism of the ancients require to be seriously refuted. Like some other philosophical paradoxes, it would have been better left to die out. It certainly could not be refuted by a philosophy such as Kant's, in which, no less than in the previously mentioned systems, the history of the human mind and the nature of language are almost wholly ignored, and the certainty of objective knowledge is transferred to the subject; while absolute truth is reduced to a figment, more abstract and narrow than Plato's ideas, of 'thing in itself,' to which, if we reason strictly, no predicate can be applied.