Now what do I want to illustrate by these three instances? The rapidity with which we are now at last throwing off the last vestiges of the yoke of Greece? No, not that. I want to point out that even in the realm of science, where progress is so swift and books so short-lived, the Greeks of the great age had such genius and vitality that their books lived in a way that no others have lived. Let us get away from the thought of Euclid as an inky and imperfect English school-book, to that ancient Eucleides who, with exceedingly few books but a large table of sand let into the floor, planned and discovered and put together and re-shaped the first laws of geometry, till at last he had written one of the great simple books of the world, a book which should stand a pillar and beacon to mankind long after all the political world that Eucleides knew had been swept away and the kings he served were conquered by the Romans, and the Romans in course of time conquered by the barbarians, and the barbarians themselves, with much labour and reluctance, partly by means of Eucleides' book, eventually educated; so that at last, in our own day, they can manage to learn their geometry without it. The time has come for Euclid to be superseded; let him go. He has surely held the torch for mankind long enough; and books of science are born to be superseded. What I want to suggest is that the same extraordinary vitality of mind which made Hippocrates and Euclid and even Denis of Thrace last their two thousand years, was also put by the Greeks of the great age into those activities which are, for the most part at any rate, not perishable or progressive but eternal. This is a simple point, but it is so important that we must dwell on it for a moment. If we read an old treatise on medicine or mechanics, we may admire it and feel it a work of genius, but we also feel that it is obsolete: its work is over; we have got beyond it. But when we read Homer or Aeschylus, if once we have the power to admire and understand their writing, we do not for the most part have any feeling of having got beyond them. We have done so no doubt in all kinds of minor things, in general knowledge, in details of technique, in civilization and the like; but hardly any sensible person ever imagines that he has got beyond their essential quality, the quality that has made them great.