The world presented for our belief by a philosophy based upon modern science is in many ways less alien to ourselves than the world of matter as conceived in former centuries. The events that happen in our minds are part of the course of nature, and we do not know that the events which happen elsewhere are of a totally different kind. The physical world, so far as science can show at present, is perhaps less rigidly determined by causal laws than it was thought to be; one might, more or less fancifully, attribute even to the atom a kind of limited free will. There is no need to think of ourselves as powerless and small in the grip of vast cosmic forces. All measurement is conventional, and it would be possible to devise a perfectly serviceable system of measurement according to which a man would be larger than the sun. No doubt there are limits to our power, and it is good that we should recognise the fact. But we cannot say what the limits are, except in a quite abstract way, such as that we cannot create energy. From the point of view of human life, it is not important to be able to _create_ energy; what is important is to be able to direct energy into this or that channel, and this can do more and more as our knowledge of science increases. Since men first began to think, the forces of nature have oppressed them; earthquakes, floods, pestilences, and famines have filled them with terror. Now at last, thanks to science, mankind is discovering how to avoid much of the suffering that such events have hitherto entailed. The mood in which, as it seems to me the modern man should face the universe is one of quiet self-respect. The universe as known to science is not in itself either friendly or hostile to man, but it can be made to act as a friend if approached with patient knowledge. Where the universe is concerned, knowledge is the one thing needful. Man, alone of living things, has shown himself capable of the knowledge required to give him a certain mastery over his environment. The dangers to man in the future, or at least in any measurable future, come, not from nature, but from man himself. Will he use his power wisely? Or will he turn the energy liberated from the struggle with nature into struggles with his fellow-men? History, science, and philosophy all make us aware of the great collective achievements of mankind. It would be well if every civilised human being had a sense of these achievements and a realisation of the possibility of greater things to come, with the indifference which must result as regards the petty squabbles upon which the passions of individuals and nations are wastefully squandered.