Any resistance we have to the deceptive worldly spirits comes not from ourselves, but through the atoning work of Jesus Christ. And no comment is necessary, since Augustine speaks quite well for himself here (as is generally the case):
...therefore he [the devil] is conquered in the name of Him who assumed humanity, and that without sin, that Himself being both Priest and Sacrifice, He might bring about the remission of sins, that is to say, might bring it about through the Mediator between God and men, the man Christ Jesus, by whom we are reconciled to God, the cleansing from sin being accomplished. For men are separated from God only by sins, from which we are in this life cleansed not by our own virtue, but by the divine compassion; through His indulgence, not through our own power. For, whatever virtue we call our own is itself bestowed upon us by His goodness. And we might attribute too much to ourselves while in the flesh, unless we lived in the receipt of pardon until we laid it down. This is the reason why there has been vouchsafed to us, through the Mediator, this grace, that we who are polluted by sinful flesh should be cleansed by the likeness of sinful flesh. By this grace of God, wherein He has shown His great compassion toward us, we are both governed by faith in this life, and, after this life, are led onwards to the fullest perfection by the vision of immutable truth.Chapter 23:
Even the pagans have some limited understanding of this, though this understanding is based on a limited rationality pursued by free speech and driven by principles, not by the strict Revelation which Christians have received concerning the truth.
Unlike the pagans (especially Porphyry), we do not hold to broad principles, but rather to Christ who died for our sins and will raise us to new life again on the last day:
Thus the good and true Mediator showed that it is sin which is evil, and not the substance or nature of flesh; for this, together with the human soul, could without sin be both assumed and retained, and laid down in death, and changed to something better by resurrection. He showed also that death itself, although the punishment of sin, was submitted to by Him for our sakes without sin, and must not be evaded by sin on our part, but rather, if opportunity serves, be borne for righteousness’ sake. For he was able to expiate sins by dying, because He both died, and not for sin of His own.This great Gospel is the means by which we are made clean, which we mystically recall in the Lord's Supper, and which the pagans deny not out of lack of understanding, but out of pride.