We have already drawn attention to the gradual escape of writing and knowledge from their original limitation to the priesthood and the temple precincts, from the shell in which they were first developed and cherished. We have taken Herodotus as an interesting specimen of what we have called the free intelligence of mankind. Now here we are dealing with a similar overflow of moral ideas into the general community. The Hebrew prophets, and the steady expansion of their ideas towards one God in all the world, is a parallel development of the free conscience of mankind. From this time onward there runs through human thought, now weakly and obscurely, now gathering power, the idea of one rule in the world, and of a promise and possibility of an active and splendid peace and happiness in human affairs. From being a temple religion of the old type, the Jewish religion becomes, to a large extent, a prophetic and creative religion of a new type. Prophet succeeds prophet. Later on, as we shall tell, there was born a prophet of unprecedented power, Jesus, whose followers founded the great universal religion of Christianity. Still later Muhammad, another prophet, appears in Arabia and founds Islam. In spite of very distinctive features of their own, these two teachers do in a manner arise out of, and in succession to these Jewish prophets. It is not the place of the historian to discuss the truth and falsity of religion, but it is his business to record the appearance of great constructive ideas. Two thousand four hundred years ago, and six or seven or eight thousand years after the walls of the first Sumerian cities arose, the ideas of the moral unity of mankind and of a world peace had come into the world.[168] XXII THE GREEKS AND THE PERSIANS[169] § 1. _The Hellenic Peoples._ § 2. _Distinctive Features of Hellenic Civilization._ § 3. _Monarchy, Aristocracy, and Democracy in Greece._ § 4. _The Kingdom of Lydia._ § 5. _The Rise of the Persians in the East._ § 6. _The Story of Crœsus._ § 7. _Darius Invades Russia._ § 8. _The Battle of Marathon._ § 9. _Thermopylæ and Salamis._ § 10. _Platæa and Mycale._ § 1 And now our history must go back again to those Aryan-speaking peoples of whose early beginnings we have given an account in Chapters XIV and XV. We must, for the sake of precision, repeat here two warnings we have already given the reader: first, that we use the word Aryan in its widest sense, to express all the early peoples who spoke languages of the “Indo-Germanic” or “Indo-European” group; and, secondly, that when we use the word Aryan we do not imply any racial purity.