This easy assumption that reality accommodates itself to our intellectual convenience, instead of our being obliged to accommodate our theories of knowledge to reality, runs through and vitiates the whole of Kant's philosophy. But, taking the narrower ground of logical consistency, one hardly sees how his principles can hold together. We are told that the subjectivity of space and time is not presented as a plausible hypothesis, but as a certain and indubitable truth, for in no other way can mathematical certainty be explained. The claim is questionable, but let it be granted. Immediately a fresh difficulty starts up. What is the source of our certainty that space and time are subjective forms of intuition? If the answer is, because that assumption guarantees the certainty of mathematics, then Kant is {92} reasoning in a circle. If he appeals--as in consistency he ought--to another order of subjectivity as the sanction of his first transcendental argument, such reasoning involves the regress to infinity. Again, on Kant's theory, time is the form of intuition for the inner sense. So when we become conscious of mental events we know them only as phenomena; we remain ignorant of what mind is in itself. But before the publication in 1770 of Kant's inaugural dissertation on _The Sensible and the Intelligible World_ every one, plain men and philosophers alike, believed that the consciousness of our successive thoughts and feelings was the very type of reality itself; and they held this belief with a higher degree of assurance than that given to the axioms of geometry. By what right, then, are we asked to give up the greater for the less, to surrender our self-assurance as a ransom for Euclid's _Elements_ or even for Newton's _Principia_? Once more, surely mathematics is concerned not with space and time as such, but with their artificial delimitations as points, lines, figures, numbers, moments, etc. And it may be granted that these are purely subjective in the sense of being imposed by our imagination (with the aid of sensible signs) on the external world. What if _this_ subjectivity were the true source of that peculiar certainty belonging to synthetic judgments _à priori_? True, Kant counts in our judgments about the infinity and eternity of space and time with other accepted characteristics of theirs as intuitive certainties. But there are thinkers who find the negation of such properties not inconceivable, so that they cannot be adduced as evidence of a priority, still less of subjectivity.