To the Greek mind two things had become clear before Christianity came into the world, and it would be easy to trace the steps by which the conclusions were reached. First, Reason, as relation-giving, seeks for unity in the manifoldness of which it is conscious, and will be satisfied with nothing less. But Eleaticism had convincingly proved that an abstract unity can explain nothing. Quite apart from questions of religion and morals, the Eleatic unity was metaphysically a failure. Plato had seen this, and yet the 'dead hand' of Eleaticism rested on Platonism, and the dialogue _Parmenides_ shewed how powerless the Doctrine of Ideas was to evade the difficulty. Thus the Greeks more than 2000 years ago had realized, what is nowadays proclaimed, as if it were a new discovery, that an absolute unit is unthinkable, because, as Plato puts it in the _Philebus_, the union of the one and the many is 'an everlasting quality in thought itself which never grows old in us.' The Greeks, like the Jews, had thus had their 'schoolmaster to bring them to Christ.' They had not solved, but they had felt, the rational difficulty; as the Jews had felt, but had not overcome, except through the Messianic hope, the separation of man from God. But as the Trinitarian doctrine took shape, Christian teachers realized how the Christian, as opposed to the Jewish, idea of God, not only held the truth of the Divine Unity as against all polytheistic religions, but claimed reason on its side against all Unitarian theories. They did not, however, argue that it was true because it satisfied reason, but that it satisfied reason because it was true. They started, indeed, not with a metaphysical problem to be solved, but with a historical fact to proclaim, the fact of the Resurrection, and a doctrinal truth to maintain, the Divinity of Him who rose. And starting from that basis of fact revealed in Christ, they found themselves in possession of an answer to difficulties which at first they had not felt, and thus their belief was justified and verified in the speculative region.