If, on the contrary, the highest ruling power in nature is an arbitrary divine caprice, if the world which lies open before mankind is ruled by another's purely fortuitous decrees, themselves interfered with continually by hostile influences from an infernal kingdom; if, moreover, this struggle rages not merely in the external world, but also in the very core of human nature, vitiating her reason, feelings and will, so to employ them without her agency as means to her exaltation or perdition, then is there indeed no causality to be sought for, and consequently no field anywhere for scientific investigation. Were there even any such thing as science, it would lie far beyond the powers of man, since reason, a mere plaything for demoniac powers, can not be trusted. Neither has his personality any longer its centre of gravity within itself. Then is man in excessive need of such an institution of deliverance as the Church, which teaches him what the divine authority has arbitrarily decided to be good or evil; while the supernatural means of grace, the sacraments, afford him power of resisting evil, and absolve him from his failings. In this way external authority supplants the inner, which is torn up by the roots. That ideal of human perfection which is possible under such conditions, and which actually arises because the native activity of the mind constantly endeavors to bring all accepted notions into union, places itself on the doctrine of authority as its foundation, and accepts its supernatural character. That the ideal of the Middle Ages is ascetic and its science magical, is directly consequent upon its dualistic conception of the universe and of its peculiar nature. The dualism of the Middle Ages was derived from Persia. It is the essential idea of the Zoroastrian doctrine, which finally, after a long struggle against the unitarian notions of the Greeks, penetrates the Occident and completely conquers it. This victorious combat of the Orient against Europe is the sum of history between Cyrus and Constantine. The external events which fill those centuries obtain their true significance when within and behind them one perceives the struggle between the two conflicting systems of ideas. Like concealed chess-players they move their unconscious champions against each other on the board of history.