The first two stages in the development of civilized man were probably the invention of primitive weapons and the discovery of fire, although nobody knows exactly when he acquired the use of the latter. The origin of language is also obscure. No doubt it began very gradually. Animals have a few cries that serve as signals, but even the highest apes have not been found able to pronounce words, even after the most intensive professional instruction. The superior brain of man is apparently a necessity for the mastering of speech. When man became sufficiently intelligent, we must suppose that he gradually increased the number of cries for different purposes. It was a great day when he discovered that speech could be used for narrative. Two important stages came not so long before the dawn of written history. The first was the domestication of animals; the second was agriculture. Agriculture was a step in human progress to which subsequently there was nothing comparable until our own machine age. Agriculture made possible an immense increase in the number of the human species in the regions where it could be successfully practiced. These were, at first, only those in which nature fertilized the soil after each harvest. Agriculture met with violent resistance from the pastoral nomads, but the agricultural way of life prevailed in the end because of the physical comforts it provided. Another fundamental technical advance was writing, which, like spoken language, developed out of pictures, but as soon as it had reached a certain stage, it was possible to keep records and transmit information to people who were not present when the information was given. These inventions and discoveries — fire, speech, weapons, domestic animals, agriculture, and writing — made the existence of civilized communities possible. From about 3000 B. C. until the beginning of the Industrial Revolution less than two hundred years ago there was no technical advance comparable to these. During this long period man had time to become accustomed to his technique, and to develop the beliefs and political organizations appropriate to it. There was, of course, an immense extension in the area of civilized life. At first it had been confined to the Nile, the Euphrates, the Tigris and the Indus, but at the end of the period in question it covered a much greater part of the inhabitable globe. I do not mean to suggest that there was no technical progress during this long time; there was progress — there were even two inventions of very great importance, namely gunpowder and the mariner’s compass — but neither of these can be compared in their revolutionary power to such things as speech and writing and agriculture.