=The Two Elements in Augustine’s Teaching.= The great masses of thought in Augustine’s mind reveal motion in two directions. On the one hand, he is the theologian who holds on high the conception of the authority of the church. On the other hand, he is the philosopher who speaks for the principle of immediate certainty for the individual. These are two foci about which his thought is in constant flux and often in contradiction. Augustine has, therefore, two criteria for truth: the truth that comes from an authority without, and the truth that comes from consciousness itself. _The authority of the church and the authority of the immediate consciousness of the individual_――these are the two central thoughts in Augustinianism. Augustine’s conception of the authority of the church acted upon him as a lofty ideal which both inspired and at the same time constrained his speculations. As he grew older he gravitated more and more toward it, and thereby became more conservative. But it was the other central thought――the authority of immediate consciousness――which he made the basis of a philosophy of original power. Through this he transcended his own time and became himself a modern, leading the Middle Ages up to him. Augustine did not define accurately the spheres of philosophy and theology. He did not show whether reason or revelation had the higher authority. He did not try to decide between the _intelligo ut credam_ and _credo ut intelligam_, that is, between the respective authorities of reason and faith. That became, in consequence, a central philosophical problem for the schoolmen. Nevertheless, the great inheritance which Augustine left the world was along the philosophical line of _intelligo ut credam_ (of knowledge as the basis of faith instead of faith as the basis of knowledge). =The Neo-Platonic Element: the Inner Certainties of Consciousness.= Augustine was not original in making the starting-point of his philosophy the inner certainties of consciousness. That was the point of view of his time, and the starting-point of the ascetic tendency both of Christianity and of neo-Platonism. He was dissatisfied with the world without, and turned away from it to the world within to find reality. But this had been a growing tendency ever since the time of Plato. Augustine’s originality lies in his psychological description of these certainties. He is the master of self-observation and introspection. He can describe inner experiences as well as analyze them. He puts his philosophy upon a solid anthropological basis by developing a psychology of the certainties of consciousness. In doing this he placed the inner experience in the central position of control. Thus he reached a well-defined position of “internality” for which the Stoics, Epicureans, neo-Platonists, and the preceding Christian theologians had been groping; thus he anticipated Descartes and modern philosophy.