If the cessation of speculative activity among the Greeks needs to be accounted for by something more definite than phrases about the objective and the subjective, so also does its resumption among the nations of modern Europe. This may be explained by two different circumstances--the disappearance of the obstacles which had long opposed themselves to the free exercise of reason, and the stimulus given to enquiry by the Copernican astronomy. After spreading over the whole basin of the Mediterranean, Hellenic culture had next to repair the ravages of the barbarians, and, chiefly under the form of Christianity, to make itself accepted by the new nationalities which had risen on the ruins of the Roman empire. So arduous a task was sufficient to engross, during many centuries, the entire intellectual energies of Western Europe. At last the extreme limits of diffusion were provisionally reached, and thought once more became available for the discovery of new truth. Simultaneously with this consummation, the great supernaturalist reaction, having also reached its extreme limits, had so far subsided, that Nature could once more be studied on scientific principles, with less freedom, indeed, than in old Ionia, but still with tolerable security against the vengeance of interested or fanatical opponents. And at the very same conjuncture it was shown by the accumulated observations of many ages that the conception of the universe on which the accepted philosophy rested must be replaced by one of a directly opposite description. I must confess that in this vast revolution the relation between the objective and the subjective, as reconstituted by Christianity and the Germanic genius, does not seem to me to have played a very prominent part.