Not that the vitality of Hellenic reason gave way simultaneously at every point. The same independent spirit, the same imaginative vigour which had carried physical speculation to such splendid conquests during the first two centuries of its existence were manifested with equal effect when the energies previously devoted to Nature as a whole concentrated themselves on the study of conduct and belief. It was thus that Socrates could claim the whole field of human life for scientific treatment, and create the method by which it has ever since been most successfully studied. It was thus that Plato could analyse and ideally reconstruct all practices, institutions, and beliefs. It was thus that Aristotle, while definitely arresting the progress of research, could still complete the method and create the language through which the results of new research have been established, recognised, and communicated ever since. It was thus that the Stoics advanced from paradox to paradox until they succeeded in co-ordinating morality for all time by reference to the three fundamental ideas of personal conscience, individual obligation, and universal humanity. And not only were dialectics and ethics at first animated by the same enterprising spirit as speculative physics, but their very existence as recognised studies must be ascribed to its decay, to the revolution through which philosophy, from being purely theoretical, became social and didactic. While in some directions thought was made stationary and even retrogressive by the very process of its diffusion, in other directions this diffusion was the cause of its more complete development. Finally, ethics and logic were reduced to a scholastic routine, and progress continued to be made only in the positive sciences, until, here also, it was brought to an end by the triumph of superstition and barbarism combined.