Such an allusion to the Romans, in an exposition like the present one, is not without its significance. It was partly through political circumstances that a truly theistic idea was developed out of the chaotic and fragmentary ghost theories and nature-worship of the primeval world. To the framing of the vastest of all possible conceptions, the idea of God, man came but slowly. This nature-worship and ancestor-worship of early times was scarcely theism. In their recognition of man's utter dependence upon something outside of himself which yet was not wholly unlike himself, these primitive religions contained the essential germ out of which theism was to grow; but it is a long way from the propitiation of ghosts and the adoration of the rising sun to the worship of the infinite and eternal God, the maker of heaven and earth, in whom we live, and move, and have our being. Before men could arrive at such a conception, it was necessary for them to obtain some integral idea of the heaven and the earth; it was necessary for them to frame, however inadequately, the conception of a physical universe. Such a conception had been reached by civilized peoples before the Christian era, and by the Greeks a remarkable beginning had been made in the generalization and interpretation of physical phenomena. The intellectual atmosphere of Alexandria, for two centuries before and three centuries after the time of Christ, was more modern than anything that followed down to the days of Bacon and Descartes; and all the leaders of Greek thought since Anaxagoras had been virtually or avowedly monotheists. As the phenomena of nature were generalized, the deities or superhuman beings regarded as their sources were likewise generalized, until the conception of nature as a whole gave rise to the conception of a single Deity as the author and ruler of nature; and in accordance with the order of its genesis, this notion of Deity was still the notion of a Being possessed of psychical attributes, and in some way like unto Man.