To some extent all philosophical systems have a place for intuition: direct knowledge that is non-inferential or cannot be proved by prior argument and for which there is no way to resolve doubts. Mill thought that William Whewell’s (1794–1866) philosophy of science was “intuitive,” although it was in places quite inferential. However, Whewell did have an explicitly intuitionist moral theory. Other noteworthy nineteenth century intuitionists were William Hamilton, F.H. Bradley, Henry Sidgwick, James Martineau, and, toward the end of the century and into the next, Henri Bergson.