WE> have seen that during the first half of the XIXth Century and for some time afterwards the dominant feature of British phirosophy was the antagonism between -the Scottish school and the traditional empiricists, and that the latter steadily gained ground. But even before this conflict, with Hamilton and Mill as its last protagonists, had been settled in favour of the latter, a new force, destined to power, had come into play, namely, the doctrines of Spencer and Darwin. It was in the 'fifties that the idea of evolution appeared in philosophy as well as in the special sciences, the decade which saw the death of Hamilton and the rise of Mill to the height of his power. The movement instigated by Spencer and Darwin was connected intimately with what we have regarded as the traditional line of British thought. Although a new and luxuriant shoot, it sprang from the same stock and had its roots in the same soil as the old empiricism. No sharp lme can be drawn between it and the movement led by Bentham and Mill; the two lines of thought cross and recross to such an extent that the assignment of a thinker to th~ evolutionist school can rest on nothing more than the predominance of the new impulse in his 'philosophy. But the new impulse soon became so powerful that from the 'sixties onwards very few thinkers were able to avoid being moved by it.