It has been mentioned how Kant's metaphysical {133} agnosticism was played out by Hamilton against Cousin. A little later Whewell, the Cambridge historian of physical science, imported Kant's theory of necessary truth in opposition to the empiricism of popular English thought, and Kant's Categorical Imperative in still more express contradiction to Bentham's utilitarian morality. Now Mill, educated as he had been on the associationist psychology and in the central line of the English epistemological tradition, rejected the German apriorism as false in itself, while more particularly hating it as, in his opinion, a dangerous enemy to all social progress. For to him what people called their intuitions, whether theoretic or practical, were merely the time-honoured prejudices in which they had been brought up, and the contradictory of which they could not conceive. Comte similarly interpreted the metaphysical stage of thought as the erection into immutable principles of certain abstract ideas whose value--if they had any--was merely relative and provisional. Mill, with his knowledge of history, might have remembered that past thought, beginning with Plato, shows no such connection between intuitionism and immobility or reaction, while such experientialists as Hobbes and Hume have been political Tories. But in his own time the _à priori_ philosophy went hand in hand with conservatism in Church and State, so he set himself to explode it in his _System of Logic_ (1843). Mill's _Logic_, the most important English contribution to philosophy since Hume, is based on Hume's theory of knowledge, amended and supplemented by some German and French ideas. It is conceded to Kant that mathematical truths are synthetic, not analytic. It is not contained in the idea of two and {134} two that they make four, nor in the idea of two straight lines that they cannot enclose a space. Such propositions are real additions to our knowledge; but it is only experience that justifies us in accepting them. What constitutes their peculiar certainty is that they can be verified by trial on imagined numbers and lines, without reference to external objects. But by what right we generalise from mental experience to all experience Mill does not explain. Hume's analysis of causation into antecedence and sequence of phenomena is accepted by Mill as it was accepted by Kant; but the law that every change must have a cause is affirmed, in adhesion to Dr. Thomas Brown (1778-1820), with more distinctness than by Hume. As Laplace put it, the whole present state of the universe is a product of its whole preceding state. But we only know this truth by experience; and we can conceive a state of things where phenomena succeed one another by a different law or without any law at all. Mill himself was ready to believe that causation did not obtain at some very remote point of space; though what difference remoteness could make,