Augustine became the Neoplatonic philosopher and he used it as the basis for a new certainty, the immediate certainty of God. In Neoplatonism you have the immediacy of truth in the inner soul, and from this he got his new certainty of the Divine, Secondly, Neoplatonism gave him the basis for his interpretation of the relationship of God and the world, God as the creative Ground of the world in terms of amor (love).
Thirdly, it gave him the entrance to himself, from a psychological point of view, although this had to be supported by his Christian experience.
But now Augustine did something which later on all Renaissance philosophers also did: he turned the meaning of Neoplatonism into its opposite. Neoplatonism was a negative philosophy, a philosophy of escape from the world. The elevation of the soul out of the material world into the Ultimate, is the meaning of Neoplatonism.
Augustine changes the emphasis. And this is the case in all Western Neoplatonism.
Therefore he dropped the idea of degrees and used Neoplatonism for the .immediate experience of the Divine in everything, but especially in his soul.
In his doctrine of sin and grace, we still have these two influences, the influence of Manichaeism in his doctrine of sin and the influence of Neoplatonism in his doctrine of grace – we will come to this later. But he overcame skepticism not only philosophically, with the help of the Neoplatonists: he also overcame it with the help of the authority of the Church, under the influence of St. Ambrose, bishop of Milano, in whom the authority of the Church was represented.
The principle of authority was a form in which the new archaism, or the new archaic period which starts with the Church tradition, became conscious .of itself.
The skeptical catastrophe drove Augustine more and more to authority, to the authority of revelation, concretely given to him by the authority of the Church, concretely given to him by the authority of this great bishop of Milano.
The whole medieval development has in its underground the anxiety of skepticism, the anxiety of meaninglessness, as we could call it, over against which the acceptance of revelation and authority stood. We can say the catastrophe of the Greek autonomous attempt to construct a world out of pure thought, is the negative presupposition of the Christian doctrine of authority. – Authority for Augustine – you know he said that he would not have believed in the Christian message without the authority of the Church – means the impressive, the imposing, the overwhelming power of the Church and its great great representatives. This element of authority was not what it is for us, a problem of heteronomy, subjectionof something to what someb0dy else says to us we should accept. But it was for him the answer to the question implied in ancient skepticism.
Therefore he did not feel it as heteronomy, he felt it as theonomy – and somehow rightly so, at that time. We will come back to this problem in the survey of the Middle Ages.