The Devil Would Be Nothing

Diabolus nihil esset, si essent sollicitores homines et cautiores. Aut quid in homine umquam praevaluit ille virtute, nisi arte, mendacio, insidiis, fraude, dolo, nequitia, vitiorum ministerio, furore criminum? Ille voluntates hominum semper explorat, et bonas quidem voluntates refugit; malis autem voluntatibus obsecundat, ut sit minister scelerum, criminum leno, parasitus ipse vitiorum. Et quia potestate non potest, dominatur turpissimus mentibus turpissima servitute. Sic mendacio decepit Evam, sic cupiditate laqueavit Judam. Sanctus Petrus Chrysologus, Sermo CV

The devil would be nothing, if men were more careful and cautious. When did he ever have such strength to prevail over a man expect by cleverness, or lies, or treachery, or fraud, or deception, or malice, or use of the vices, or by the madness of sins? He always examines the wills of men, and flies from the good will, but he cleaves to bad wills, that he be a servant of wickedness, a procurer of sins, a parasite of vices. And since alone he is powerless, he rules over the most despicable minds in the most despicable slavery. So he deceived Eve with a lie  and snared Judas with greed. Saint Peter Chrysologus, from Sermon 105