Thomas Aquinas Commentary Galatians 5:16-17

"But I say, walk by the Spirit, and ye shall not fulfil the lust of the flesh. For the flesh lusteth against the Spirit, and the Spirit against the flesh; for these are contrary the one to the other; that ye may not do the things that ye would." — Galatians 5:16-17 (ASV)

After indicating that the spiritual state consists in charity, the Apostle then deals with the cause of this state: the Holy Spirit, whom he says they must follow. He then mentions three benefits obtained from the Holy Spirit.

1. Freedom from the bondage of the flesh.
2. Freedom from the bondage of the Law (Galatians 5:18).
3. The conferring of life, or security from the damnation of death (Galatians 5:25).

Regarding the first point, he does two things:

1. He presents the first benefit of the Spirit.
2. He shows the need for this benefit (Galatians 5:17).

Therefore, he says: I say that you are obliged by the charity of the spirit to serve one another, because nothing profits without charity. But this I say in Christ—by the faith of Christ—walk in the spirit. This can be understood first as walking in the mind and reason, for our mind is sometimes called a spirit, according to Ephesians 4:23: Be renewed in the spirit of your mind, and 1 Corinthians 14:15: I will sing with the spirit, I will sing also with the understanding.

Alternatively, to “walk in the spirit” means to make progress in the Holy Spirit by acting well. For the Holy Spirit moves and prompts hearts to do good: Whosoever are led by the Spirit of God, they are the sons of God (Romans 8:14). One should, therefore, walk by the spirit—that is, the mind—so that one’s reason or mind is in accord with the Law of God, as it is said in Romans 7:16.

For the human spirit is fickle. Unless it is governed from an outside source, it turns now in one direction and now in another, as is said in Sirach 34:6: The heart fancieth as that of a woman in travail. Except it be a vision sent forth from the most High, set not thy heart upon them. For this reason, Ephesians 4:17 says of certain people: They walk in the vanity of their mind. Therefore, human reason cannot stand perfectly unless it is governed by a divine spirit.

Accordingly, the Apostle says to walk in the spirit, meaning under the rule and guidance of the Holy Spirit, whom we should follow as a guide pointing out the way. For knowledge of the supernatural end is in us only from the Holy Spirit: Eye hath not seen nor ear heard, neither hath it entered into the heart of man what things God hath prepared for them that love Him. And immediately he adds, But to us God hath revealed them by his Spirit (1 Corinthians 2:9).

We should also follow the Spirit as one who inclines us. For the Holy Spirit stirs up and turns our affections toward willing what is right: Whosoever are led by the Spirit of God, they are the sons of God (Romans 8:14); Thy good spirit shall lead me into the right land (Psalms 142:10).

Now, one should walk in the spirit because it frees a person from the defilement of the flesh. Therefore, the Apostle continues: and you shall not fulfil the lusts of the flesh, meaning the pleasures that the flesh suggests. This is what the Apostle yearned for, saying: Unhappy man that I am, who shall deliver me from the body of this death? (Romans 7:24). Later he concludes: There is now therefore no condemnation to them that are in Christ Jesus, who walk not according to the flesh (Romans 8:1). And at once he gives the reason for this: For the law of the spirit of life in Christ Jesus hath delivered me from the law of sin and of death (Romans 8:2).

This is the special desire of the saints: that they not fulfill the desires to which the flesh stirs them. It must always be understood, however, that this does not include desires related to the necessities of the flesh, but only those related to excesses.

Then, when he says, For the flesh lusteth against the spirit, he explains why this benefit is needed, namely, because of the struggle between the flesh and the spirit.

1. He asserts that there is a struggle.
2. He elucidates this by an obvious sign (Galatians 5:17).

Therefore, he says: It is necessary that by the spirit you overcome the desires of the flesh, for the flesh lusteth against the spirit. But a doubt might arise here, because since lusting is an act of the soul alone, it does not seem to come from the flesh. I answer that, according to Augustine, the flesh is said to lust insofar as the soul lusts through the flesh, just as the eye is said to see when, in fact, it is the soul that sees through the eye.

Consequently, the soul lusts through the flesh when it seeks pleasurable things according to the flesh. But the soul lusts through itself when it takes pleasure in things that are according to the spirit, such as virtuous works, contemplation of divine things, and meditation on wisdom: The desire of wisdom bringeth to the everlasting kingdom .

But if it is the soul that lusts through the flesh, how does the flesh lust against the spirit? It does so in the sense that the lusting of the flesh hinders the desires of the spirit. For since the pleasures of the flesh concern goods that are beneath us, whereas the pleasures of the spirit concern goods that are above us, when the soul is occupied with the lower things of the flesh, it is withdrawn from the higher things of the spirit.

But his further statement that the spirit lusts against the flesh may raise a problem. For if we take “spirit” to mean the Holy Spirit, and the desire of the Holy Spirit is against evil things, it seems to follow that the flesh against which the spirit lusts is evil—which is the Manichean error. I answer that the spirit does not lust against the nature of the flesh, but against its desires, namely, those that concern excesses. For this reason he said above, you shall not fulfil the lusts of the flesh (Galatians 5:16), meaning superfluous things. For in necessary things the spirit does not contradict the flesh, as we are told in Ephesians 5:29: No man hateth his own flesh.

Then when he says, For these are contrary one to another, he gives evidence of the struggle. It is as if to say: It is obvious from experience that they fight and struggle against one another, to such an extent that you do not—that is, are not permitted to do—the things, good or evil, that you wish: The good which I will I do not: but the evil which I will not, that I do (Romans 7:19).

However, free will is not taken away. For since free will consists in having choice, there is freedom of the will with respect to things subject to choice. But not all that lies in us is fully subject to our choice, but only in a qualified sense. In specific cases we are able to avoid this or that movement of lust or anger, but we cannot avoid all movements of anger or lust in general—and this is by reason of the “fomes” introduced by the first sin.

Here it should be noted that with respect to lusts, there are four categories of people who do not do what they wish. The intemperate, who deliberately follow the passions of the flesh—according to Proverbs 2:14: They are glad when they have done evil—do, indeed, what they will, insofar as they follow their passions; but insofar as their reason complains and is displeased, they are doing what they do not wish.

Incontinent persons, who resolve to abstain but are nevertheless conquered by their passions, do what they do not wish, insofar as they follow such passions contrary to what they resolved. Between these two types, the intemperate person does more of what he wishes.

Those who are continent, who would prefer not to lust at all, do what they intend as long as they are not subject to lust; but because they cannot completely repress lust, they do what they do not wish.

Finally, those who are temperate do what they wish, insofar as there is no lust in their tamed flesh. But because the flesh cannot be totally tamed so as never to rise up against the spirit—just as malice can never so abound that reason would never complain—in those instances in which they do lust, they are doing what they do not wish. For the most part, however, they do what they wish.