4117. It is clear that conviction in bodily life is able to tame the passions, as, for example, when someone is convinced that a certain food is more nutritious than another, even if it is in itself tasteless, or tastes so bad that while before he arrived at that conviction it had tasted disgusting, he eventually prefers it, and it has a pleasing taste, so that he now prefers a bad and bitter taste to a pleasant one. In this way, one tames a passion, and so also in other cases.
The life of passion, on the other hand, usually and in most cases brings on conviction, for that which is loved immoderately is confirmed in many ways until the person becomes convinced: which can be illustrated and confirmed in innumerable cases.
4117. It may be manifest that persuasion, in the life of the body, is able to subdue cupidities, as, for example, when anyone persuades himself that a particular kind of food is more wholesome than another, although it may be of no taste at all, or of a disagreeable taste, so that previous to the persuasion he may have actually nauseated it; still he gives it the preference, and in process of time it becomes palatable to him, and even agreeable, so that he is able to prefer the nauseous and the bitter to the sweet. Thus he subdues cupidity; and similar is the case in other things. The life of cupidities, however, acts in a great measure to induce persuasion; for that which is loved perniciously is confirmed on many grounds, even until the man is persuaded, which might be illustrated and established by innumerable proofs.
4117. Constare potest, quod persuasio in vita corporis domare possit cupiditates, sicut pro exemplo, cum quis sibi persuadet, quod hic cibus, sit plus salutifer quam alius, tametsi in se nullius saporis est, et saporis tetri, sic ut priusquam persuasio venit, nauseaverit istum, usque tamen praefert, et temporis tractu ei sapit, et quidem jucunde, sic ut praeferat tetrum et amarum dulci; ita domat cupiditatem: sic in omnibus caeteris, vita cupiditatis vero, solet utplurimum inducere persuasionem; nam quod amatur perdite, confirmatur multis usque dum persuadetur homo: quod innumeris illustrari et confirmari potest.