The vogue of that style of philosophy which was founded on the tradition of speculation and honeycombed with presuppositions, did not pass out until the advent of Darwin's evolutionism. But even the inauguration of biology and sociology did not entirely eliminate the metaphysical assumption from constructive thinking. The scientists themselves, not excluding Darwin, hesitated to acknowledge the laws of natural selection and of the survival of the fit. Neo-Lamarckism was but one of the reactions against this tough and unpleasant theory. Alfred Russel Wallace and, to take an even more significant figure, Herbert Spencer, endeavoured to refute the possibility of a biological basis in thought and thus to avoid an acquiescence to the Darwinian research. John Fiske, an avowed evolutionist, indirectly repudiated the scientific origin of philosophy; and likewise most of the lesser thinkers, following the exposition of Darwin's theories, refused to apply to man the biological laws governing the animal kingdom. Balfour and Huxley sensed the incongruities and variances in this new mode of thinking, and strove to bridge the chasm between natural science and human conduct, and to construct a system of ethics which would possess a logical and naturalistic foundation. But in both cases the question was begged. We find Balfour building up a moral system which, while it did not deny Darwinism, had for its end the destruction, or at least the alteration, of natural laws. And Huxley defines human progress as an overcoming of biological principles. Thus, even in the most materialistic of physio-psychologists, the subjugation of natural laws was the primary thesis. Biology, therefore, instead of being used as a basis to further philosophy, was considered an obstacle which philosophy had to overcome.