Augustine shows clearly the religious character of sin. Sin for him is not a moral failure; it is not even disobedience. Disobedience is a consequence but not the cause. The cause is: turning away from God, and from God as the highest good, as the love with which God loves Himself, through us. For this reason, since sin has this character — if you say “sins”, it is easily dissolved into moral sins; but sin is first of all basically the power of turning away from God. For this very reason, no moral remedy is possible. Only one remedy is possible: return to God. But this of course is possible only in the power of God, and this power is lost. This is the state of man under the conditions of existence.

…Paul Tillich (1886-1965), A History of Christian Thought [1968]