Galatians 5:17

For the flesh... — In this verse we have brought out most distinctly the antithesis between the flesh and the Spirit, which is one of the root ideas in the psychology of St. Paul. It does not amount to dualism, for the body, as such, is not regarded as evil. There is nothing to show that St. Paul considered matter in itself evil. But the body becomes the seat of evil; from it arise those carnal impulses which are the origin of sin. And it is the body, looked at in this light, which is designated as “the flesh.” The flesh is the body, as animated by an evil principle. It thus becomes opposed to the good principle: whether the good principle in itself — the Spirit of God, or that organ in which the good principle resides — the spirit in man.

So that ye cannot do the things that ye would. — The opposition between the flesh and the Spirit, each pulling a different way, prevents the will from acting freely. For a full comment on this, see Romans 7:15; Romans 7:25.