Anti-pelagian Writings by St. Augustine
(3.) The Third Breviate.
III. |Again we must ask,| he says, |what sin is, -- natural? or accidental? If natural, it is not sin; if accidental, it is separable; and if it is separable, it can be avoided; and because it can be avoided, man can be without that which can be avoided.| The answer to this is, that sin is not natural; but nature (especially in that corrupt state from which we have become by nature |children of wrath| ) has too little determination of will to avoid sin, unless assisted and healed by God's grace through Jesus Christ our Lord.