The conception of science as a body of thought embracing the whole of our rational convictions about reality has hardly yet been generally reached. Man is still so far from being a rational animal that the application of rational methods of inquiry to all branches of his experience is still instinctively resisted--as if reason were an alien and hostile intruder. Beliefs which are held with passion, being the expression of instinctive preferences, are felt not to belong to the “sphere” of science. On all questions where his passions are strongly engaged, man prizes certitude and fears knowledge. Dispassionate inquiry is welcomed only when the result is indifferent. Nearly every great scientific generalisation has incurred the _odium theologicum_--which is not the exclusive possession of theologians--from the Copernican hypothesis to the theory of herd instinct. That science, although continually wounding men, should nevertheless have progressed, is evidence that it serves impulses deeply rooted in man’s nature. The great scientific innovator, like the great altruist, is treated with ignominy by the society whose deepest instincts he lives to serve. Science, the child of irrational impulse, has inherited something of the parental character. Its history reveals it as purblind and fumbling, with no clear vision of its aim, no premonition of its imperial state. Unlike philosophy, it did not aspire to universal dominion. It was content to investigate the particular instance, and did not reject a certain incoherence in explanation rather than accept a generalisation which did not spring from its own ground. It refused foreign assistance, but kept its independence. That scientific men did not always understand that science must, from its nature, be autonomous, is evident from the history of every particular science. Even as late as Descartes it was considered quite natural to deduce phenomena from metaphysical principles; and an admixture of mythical elements is not entirely absent from some branches of science, even at the present day. Science has not yet reached full consciousness of its proper ground and aims.