The Celts may have had much in common with the Cymri, but their constitution was peculiar to them; we have no proof to show that what Caesar says about them also applies to the Belgae. The existence of an aristocratic constitution, which, in the case of many other nations is assumed only from misinterpreted expressions, cannot be doubted among the Celts. We find among them two ruling tribes, the knights and the priests, the well-known Druids; the rest of the people were mere serfs. This circumstance, as I have observed on other similar occasions, intimates that the Celts, in the countries where we know them, were conquering foreigners, and that the power which drove them out of Spain, led them into a country, where, in their turn, they subdued other people. My conjecture is, that this latter people, extending over nearly the whole of France, was no other than the Cymri, who, being pressed by the Celts, advanced northward, and threw themselves upon German tribes; and this circumstance produced the mixture of Belgae and Germans in the north. It is well known that the Druids were a caste,[71] but it is impossible to ascertain whether the Druids and knights were two different castes, like the Brahmins and warriors in India, or whether the Druids were only a branch of the military caste, which occupied itself with matters of religion. Certain it is, however, that all the power was divided between these two, while the people lived in a condition which Caesar describes by the term _clientela_, that is, bondage. It was not exactly what we call serfdom; for the Celtic people were dependent only in relation to their feudal lords, whose retinue they formed, but in other respects they were free; and besides them, slaves are expressly mentioned. The religion of the Druids was bloody and cruel, and for this reason it was the only one that was attacked by the Romans; though they may have done so also because that religion formed an obstacle to the Romanising of Gaul. Success was not difficult, and the Druids were completely crushed. It is possible that some of the later commotions of which we read in Tacitus, as, e.g., those of Sacrovir and Classicus, may have been connected with religion. The Druids also were the depositories of a kind of science and literature, for they had poems which it was unlawful to commit to writing. In the transactions of ordinary life, they used the Greek alphabet.