Necessarily polytheistic in its origins, religion tended nevertheless towards monotheism. The subordination which disciplined the heads of the tribes on earth also ranged the divinities under the authority of a supreme head. Force at first gave this supremacy. Zeus was the king of gods and men because he was stronger than all of them put together. This is the natural order of ideas. Force first imposed itself on weakness; then intelligence conquered force; lastly, justice and love, which is the supreme form and flower of righteousness, obtain supremacy over intelligence itself. The highest and the chiefest is no longer the strongest, or the wisest, but the best. In becoming moral, man has moralised his gods, who, in their turn, becoming models and authorities, have greatly helped to moralise the race. It is very surprising that this evolution in the direction of moral monotheism did not complete itself in the Indo-European family. But the fact is that that family encountered an invincible barrier in the very nature of its primitive mythology. The Greek and Hindu philosophers, no doubt, pushed the notion of God to that of His spirituality and unity, but they did not succeed in transforming the religion of their race. Their rational criticism had power to dissolve, but not to change. Their monotheism remained always an object of speculation more or less esoteric. When, in the second and third centuries of our era, in competition with Christianity, Graeco-Roman polytheism endeavoured to reach a sort of monotheism, it could only return to the most glorious mythus of its infancy, to the worship of the Sun, and raise it to supremacy among the symbols of their faith.