Let us carry ourselves back in imagination to the state of philosophy which existed at Athens in the time of the Emperor Hadrian, and which Mr Merivale has so pleasantly described in his last volume of ‘The History of the Romans under the Empire.’ Philosophy seems to have come to a dead-lock. “On every side it was tacitly acknowledged that the limits of each specific dogma had been reached; that all were true enough to be taught, and none so true as to be exclusively believed. Their several professors lived together in conventional antagonism, and in real good-fellowship. Academics and Peripatetics, Stoics and Epicureans, Pyrrhonists and Cynics, disputed together or thundered one against the other through the morning, and bathed, dined, and joked together, with easy indifference, through the evening.” Well, let us suppose that amongst this conclave a Baconian philosopher had presented himself, with his new _organon_ and his speculations on the new power men would derive, if, with this _organon_ in their hands, they would proceed to the study of nature. After some struggle to get a footing in what Mr Merivale has described as a most conservative university, he would perhaps have been allowed to open his school in Athens, and he would have added one more figure to that group of philosophers who disputed in the morning, and dined amicably together in the evening. Another admirable talker would have appeared amongst them. This would have been the whole result. But now let us imagine that to this Athens a Galileo had come with his telescope and revealed the satellites of Jupiter; let us imagine that a Cavendish had come with his electric battery and decomposed water into two gases, one of which burst readily into flame; what a stir would there then have been amongst all the schools and classes of Athens! Still larger telescopes would have been made, and the electric battery applied to all sorts of substances. An era of experimental philosophy would at once have been inaugurated.