It has sometimes been said that Kant settled this controversy between the old departments of philosophy and the new branches of science. And the settlement, it is implied, consisted in assigning to the philosopher a sort of police and patrol duty in the commonwealth of science. He was to see that boundaries were duly respected, and that each science kept strictly to its own business. For this purpose each branch of philosophy was bound to convert itself into a department of criticism—an examination of first principles in the several provinces of reality or experience—with a view to get a distinct conception of what they were, and thus define exactly the lines on which the structures of more detailed science could be put up solidly and safely. This plan offered tempting lines to research, and sounded well. But on further reflection there emerge one or two difficulties, hard to get over. Paradoxical though it may seem, one cannot rightly estimate the capacity and range of foundations, before one has had some familiarity with the buildings erected upon them. Thus you are involved in a circle: a circle which is probably inevitable, but which for that reason it is well to recognise at once. Then—what is only another way of saying the same thing—it is impossible to draw an inflexible line between premises of principle and conclusions of detail. There is no spot at which criticism can stop, and, having done its business well, hand on the remaining task to dogmatic system. It was an instinctive feeling of this implication of system in what professed only to be criticism which led the aged Kant to ignore his own previous professions that he offered as yet no system, and when Fichte maintained himself to be erecting the fabric for which Kant had prepared the ground, to reply by the counter-declaration that the criticism was the system—that “the curtain was the picture.”