This study looks into how and why Saint Augustine has formulated the notion of inwardness. I have started from the hypothesis that inwardness is the result of Augustine's search for truth. For this reason he had initially to refute skepticism in order to come to the formulation of the proto- cogito, which has not only assured him of the certainty of his own existence, but it has also indicated that it is in the inner man, in his soul, that truth should be found. For truth to be known, however, Saint Augustine has had to produce the conditions that allowed for the possibility of knowledge, which he has done in his doctrine of illumination. It is believed that through illumination, man has been created with a natural light which is able to know the eternal reasons and truth. But in De Trinitate Augustine will postulate that it is in the interior of man that God's image can be found. So if inwardness is initially thought of by Augustine as relating to epistemological order, it will, however, be formulated in a way that it also tackles ethical questions, of which Salvation is part. It can, thus, be stated that inwardness is for Augustine a notion that will be reformulated, in a way that new contents are enhanced, coming to point that, in his mature work, it acquires more and more theological characteristics.