His great service to the cause of Christian theology, and therefore to the Church universal, was his exposition of the logical results of the Nominalism of Roscelin,--to whom universals, or ideas, were merely creations of the mind, or conventional phrases, having no real existence. Hence such things as love, friendship, beauty, justice, were only conceptions. Plato and Augustine maintained that they are eternal verities, not to be explained by definitions, appealing to consciousness, in the firm belief in which the soul sustains itself; that there can be no certain knowledge without a recognition of these; that from these only sound deductions of moral truth can be drawn; that without a firm belief in these eternal certitudes there can be no repose and no lofty faith. These ideas are independent of us. They do not vary with our changing sensations; they have nothing to do with sensation. They are not creations of the brain; they inherently exist, from all eternity. The substance of these ideas is God; without these we could not conceive of God. Augustine especially, in the true spirit of Platonism, abhorred doctrines which made the existence of God depend upon our own abstractions. To him there was a reality in love, in friendship, in justice, in beauty; and he repelled scepticism as to their eternal existence, as life repels death. Roscelin took away the platform from whose lofty heights Socrates and Plato would survey the universe. He attacked the citadel in which Augustine intrenched himself amid the desolations of a dissolving world; he laid the axe at the root of the tree which sheltered all those who would fly from uncertainty and despair. But if these ideas were not true, what was true; on what were the hopes of the world to be based; where was consolation for the miseries of life to be found? "There are many goods," says Anselm, "which we desire,--some for utility, and others for beauty; but all these goods are relative,--more or less good,--and imply something absolutely good. This absolute good--the _summum bonum_--is God. In like manner all that is great and high are only relatively great and high; and hence there must be something absolutely great and high, and this is God. There must exist at least one being than which no other is higher; hence there must be but one such being,--and this is God." It was thus that Anselm brought philosophy to the support of theology. He would combat the philosophical reasonings of Roscelin with still keener dialectics. He would conquer him on his own ground and with his own weapons.