Sin is looking for the right thing in the wrong place.

I inquired what wickedness is, and I didn't find a substance, but a perversity of will twisted away from the highest substance – You oh God – towards inferior things, rejecting its own inner life and swelling with external matter.

He that becomes protector of sin shall surely become its prisoner.

There is no sin unless through a man's own will, and hence the reward when we do right things also of our own will."

(Against Fortunatus)

When I then turned toward the scriptures, they appeared to me to be quite unworthy to be compared with the dignity of Tully. For my inflated pride was repelled by their style, nor could the sharpness of my wit penetrate their inner meaning. Truly they were of a sort to aid the growth of little ones, but I scorned to be a little one and, swollen with pride, I looked upon myself as fully grown.

Forgiveness is the remission of sins. For it is by this that what has been lost, and was found, is saved from being lost again.