For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would.
For - the reason why walking by the Spirit will exclude fulfilling the lasts of the flesh; namely, their mutual contrariety.
The Spirit - not "lusteth," but 'tendeth (or, some such word) against the flesh.'
So that ye cannot do (so as to be an obstacle to your doing) the things that ye would. The Spirit (in the beginning stage of one's repentance) strives against the flesh and its evil influence; the flesh against the Spirit and His good influence; so that neither the one nor the other can be fully carried out into action. "But" (Galatians 5:18) where "the Spirit" prevails, the struggle no longer continues doubtful (Romans 7:15-20). The Greek is, 'that ye may not do whatsoever things ye would.' 'The flesh and Spirit are contrary one to the other,' so that you must not fulfill what you desire according to the carnal self, but what the Spirit within you desires (Neander). But the antithesis of Galatians 5:18 ("But," etc.), where the conflict is decided, shows, I think, that Galatians 5:17 contemplates the inability both for fully accomplishing the good we "would," owing to the opposition of the flesh, and for doing the evil our flesh would desire, owing to the opposition of the Spirit in the awakened man (such as the Galatians are assumed to be), until we yield ourselves wholly by the Spirit to 'walk by the Spirit' (Galatians 5:16; Galatians 5:18).