The second great event which we have to note is that when the Greek mind had thus been for three hundred years in possession of society throughout the East, the Roman empire came to bind in unity of government not only all those races which the successors of Alexander had ruled, but the wide regions of the West as well, and their yet uncivilised inhabitants. Here, again, the Greek mind was not dethroned, but married, as it were, to Roman power. Philosophy made a sort of triumphal entry into Rome in spite of Cato and all the conservative force of the old Roman spirit. And if fusion had been the thought, the desire, and the attempt of the Ptolemies and the Seleucidæ, even more certainly was it the only spirit by which Augustus and Tiberius could hope to rule in peace the world made subject to them. And not less than the extinction of Greek autonomy did the loss of self-government accompanying the institution of the empire force the Roman also back upon himself. When Cicero could no longer sway the senate, he studied philosophic systems at Tusculum: and certainly his book of Offices has been more valued by all posterity than his speeches against Catiline or his defence of Milo. A long train of writers from the Fathers downwards have seen in the civil unity of the Roman empire a providential preparation for a great religion. But the field on which that empire arose had already, so far as concerns the thinking classes, long been occupied by the Greek philosophy. The two forces come into operation now together: and seventy years after the battle of Actium, when Augustus and Tiberius had completely established one ruling authority, and when this second outward revolution had had full time to give its impulse to thought, and had set before the eyes of men for two whole generations the vision of an empire which seemed conterminous with civilisation itself, we may fairly ask what philosophy had done towards producing a corresponding unity of doctrine, and a society sustaining and propagating it.