It is not till after the outburst of science in the fifteenth and sixteenth centuries, after that reawakening of the hopes of human powers which takes our minds back to the Greeks, that we find the conception of Humanity appearing in something like the form in which we can now imagine it. It will have been gathered from our chapter on Science and Philosophy how essential is the growth of organized thought to the realization of any unity in a progressive world. For the realm of thought is the only one in which no distinctions of race or nation are possible, but it must be thought in which agreement is reached. So long as men can differ, as they still do, on questions of human affairs, politics, social arrangements, or even archaeological matters where race or national predominance is involved, so far science does not exert her unifying sway. But in mathematics, physics, chemistry, all the matters in which it is impossible for a man to take another view because he is a Frenchman or a German--here we reach a haven of intellectual peace; and these calm waters are spreading over the world, in spite of the tempests. To return to the educational point from which we started, we can see now another line of approach to unity in training our own minds and those of others. In some respects it is a surer way, though less direct. When studying the political life and history of other nations, even if we do so deliberately in order to find out what we owe to them, we are bound to be arrested here and there by things that we do not like, even among our best friends. The French may seem frivolous or less self-restrained than ourselves; they have had their sanguinary outbursts of revolution. Where they have impeded our own movements, as in colonization, we are the more conscious of their faults. Or we may feel that Americans have their materialistic vein. And so on. This with our best friends, who, no doubt, feel the same about us. But on the other line of approach, the study of the things on which men now agree without question, which they have built up steadily with co-operating hands, the mental effect is quite different. The opening vista leads us on, with growing admiration and confidence in the unbreakable solidarity of mankind. We know that Newton who completes Galileo, Maxwell who follows Laplace, Helmholtz who uses the results of Joule, can have no conflicting jealousies. Here quite obviously and indisputably all are fellow-workers, and before the greatness of their work the passions of rival domination in material things, the differences of national taste and habit, the quarrels of the past or the future, appear contemptible and insignificant.