Here some make the charge that the Apostle has divided man into two parts, and that he states the essence of which he is compounded to be conflicting with itself, and that the body has a contest with the soul. But this is not so, most certainly; for by “the flesh,” he does not mean the body; if he did, what would be the sense of the clause immediately following, “for it lusts,” he says, “against the Spirit?” yet the body moves not, but is moved, is not an agent, but is acted upon. How then does it lust, for lust belongs to the soul not to the body, for in another place it is said, “My soul longs,” and, “Whatsoever your soul desires, I will even do it for you,” and, “Walk not according to the desires of your heart,” and, “So pants my soul.” Wherefore then does Paul say, “the flesh lusts against the Spirit?” he is wont to call the flesh, not the natural body but the depraved will, as where he says, “But you are not in the flesh, but in the Spirit,” and again, “They that are in the flesh cannot please God.” What then? Is the flesh to be destroyed? Was not he who thus spoke clothed with flesh? Such doctrines are not of the flesh, but from the Devil, for “he was a murderer from the beginning.” What then is his meaning? It is the earthly mind, slothful and careless, that he here calls the flesh, and this is not an accusation of the body, but a charge against the slothful soul. The flesh is an instrument, and no one feels aversion and hatred to an instrument, but to him who abuses it. For it is not the iron instrument but the murderer, whom we hate and punish. But it may be said that the very calling of the faults of the soul by the name of the flesh is in itself an accusation of the body. And I admit that the flesh is inferior to the soul, yet it too is good, for that which is inferior to what is good may itself be good, but evil is not inferior to good, but opposed to it. Now if you are able to prove to me that evil originates from the body, you are at liberty to accuse it; but if your endeavor is to turn its name into a charge against it, you ought to accuse the soul likewise. For he that is deprived of the truth is called “the natural man.” and the race of demons “the spirits of wickedness.”
Again, the Scripture is wont to give the name of the Flesh to the Mysteries of the Eucharist, and to the whole Church, calling them the Body of Christ. Nay, to induce you to give the name of blessings to the things of which the flesh is the medium, you have only to imagine the extinction of the senses, and you will find the soul deprived of all discernment, and ignorant of what it before knew. For if the power of God is since “the creation of the world clearly seen, being perceived through the things that are made,” how could we see them without eyes? And if “faith comes of hearing,” how shall we hear without ears? And preaching depends on making circuits wherein the tongue and feet are employed. “For how shall they preach, except they be sent?” In the same way writing is performed by means of the hands. Do you not see that the ministry of the flesh produces for us a thousand benefits? In his expression, “the flesh lusts against the Spirit,” he means two mental states. For these are opposed to each other, namely virtue and vice, not the soul and the body. Were the two latter so opposed they would be destructive of one another, as fire of water, and darkness of light. But if the soul cares for the body, and takes great forethought on its account, and suffers a thousand things in order not to leave it, and resists being separated from it, and if the body too ministers to the soul, and conveys to it much knowledge, and is adapted to its operations, how can they be contrary, and conflicting with each other? For my part, I perceive by their acts that they are not only not contrary but closely accordant and attached one to another. It is not therefore of these that he speaks as opposed to each other, but he refers to the contest of bad and good principles. To will and not to will belongs to the soul; wherefore he says, “these are contrary the one to the other,” that you may not suffer the soul to proceed in its evil desires. For he speaks this like a Master and Teacher in a threatening way.
Ver. 18. “But if you are led by the Spirit, you are not under the Law.”
If it be asked in what way are these two connected, I answer, closely and plainly; for he that has the Spirit as he ought, quenches thereby every evil desire, and he that is released from these needs no help from the Law, but is exalted far above its precepts. He who is never angry, what need has he to hear the command, You shall not kill? He who never casts unchaste looks, what need has he of the admonition, You shall not commit adultery? Who would discourse about the fruits of wickedness with him who had plucked up the root itself? For anger is the root of murder, and of adultery the inquisitive gazing into faces. Hence he says, “If you are led by the Spirit, you are not under the Law;” wherein he appears to me to have pronounced a high and striking eulogy of the Law, if, at least, the Law stood, according to its power, in the place of the Spirit before the Spirit's coming upon us. But we are not on that account obliged to continue apart with our schoolmaster. Then we were justly subject to the Law, that by fear we might chasten our lusts, the Spirit not being manifested; but now that grace is given, which not only commands us to abstain from them, but both quenches them, and leads us to a higher rule of life, what more need is there of the Law? He who has attained an exalted excellence from an inner impulse, has no occasion for a schoolmaster, nor does any one, if he is a philosopher, require a grammarian. Why then do you so degrade yourselves, as now to listen to the Law, having previously given yourselves to the Spirit?
Ver. 19, 20, 21. “Now the works of the flesh are manifest, which are these; fornication, uncleanness, lasciviousness, idolatry, sorcery, enmities, strife, jealousies, wrath, factions, divisions, heresies, envyings, drunkenness, revellings, and such like: of the which I forewarn you even as I did forewarn you, that they which practice such things shall not inherit the kingdom of God.”
Answer me now, you that accusest your own flesh, and supposest that this is said of it as of an enemy and adversary. Let it be allowed that adultery and fornication proceed, as you assert, from the flesh; yet hatred, variance, emulations, strife, heresies, and witchcraft, these arise merely from a depraved moral choice. And so it is with the others also, for how can they belong to the flesh? You observe that he is not here speaking of the flesh, but of earthly thoughts, which trail upon the ground. Wherefore also he alarms them by saying, that “they which practice such things shall not inherit the kingdom of God.” If these things belonged to nature and not to a bad moral choice, his expression, “they practice,” is inappropriate, it should be, “they suffer.” And why should they be cast out of the kingdom, for rewards and punishments relate not to what proceeds from nature but from choice?
Ver. 22. “But the fruit of the Spirit is love, joy, peace.”
Source: Commentary on Galatians (New Advent)