Objection 1:  It would seem that without grace man can avoid sin.  Because “no one sins in what he cannot avoid,” as Augustine says (De Duab.  Anim. x, xi; De Libero Arbit. iii, 18).  Hence if a man in mortal sin cannot avoid sin, it would seem that in sinning he does not sin, which is impossible.

Obj. 2:  Further, men are corrected that they may not sin.  If therefore a man in mortal sin cannot avoid sin, correction would seem to be given to no purpose; which is absurd.

Obj. 3:  Further, it is written (Ecclus. 15:18):  “Before man is life and death, good and evil; that which he shall choose shall be given him.”  But by sinning no one ceases to be a man.  Hence it is still in his power to choose good or evil; and thus man can avoid sin without grace.

On the contrary, Augustine says (De Perfect Just. xxi):  “Whoever denies that we ought to say the prayer ‘Lead us not into temptation’ (and they deny it who maintain that the help of God’s grace is not necessary to man for salvation, but that the gift of the law is enough for the human will) ought without doubt to be removed beyond all hearing, and to be anathematized by the tongues of all.”

I answer that, We may speak of man in two ways:  first, in the state of perfect nature; secondly, in the state of corrupted nature.  Now in the state of perfect nature, man, without habitual grace, could avoid sinning either mortally or venially; since to sin is nothing else than to stray from what is according to our nature—­and in the state of perfect nature man could avoid this.  Nevertheless he could not have done it without God’s help to uphold him in good, since if this had been withdrawn, even his nature would have fallen back into nothingness.

But in the state of corrupt nature man needs grace to heal his nature in order that he may entirely abstain from sin.  And in the present life this healing is wrought in the mind—­the carnal appetite being not yet restored.  Hence the Apostle (Rom. 7:25) says in the person of one who is restored:  “I myself, with the mind, serve the law of God, but with the flesh, the law of sin.”  And in this state man can abstain from all mortal sin, which takes its stand in his reason, as stated above (Q. 74, A. 5); but man cannot abstain from all venial sin on account of the corruption of his lower appetite of sensuality.  For man can, indeed, repress each of its movements (and hence they are sinful and voluntary), but not all, because whilst he is resisting one, another may arise, and also because the reason is not always alert to avoid these movements, as was said above (Q. 74, A. 3, ad 2).