Habitus virtutis, et eadem ratione alius habitus, non causatur per unum actum, quia habitus per actum generatur inquantum potentia passiva movetur ab aliquo principio activo; ad hoc autem quod aliqua qualitas causetur in passivo, oportet quod activum totaliter vincat passivum.
A habit of virtue, and for the same reason, other habits, is not caused by one act, because a habit is generated by act inasmuch as a passive power is moved by some active principle; but in order that some quality be caused in that which is passive, the active principle must entirely overcome the passive.
Manifestum est autem quod principium activum quod est ratio, non totaliter potest supervincere appetitivam potentiam in uno actu, eo quod appetitiva potentia se habet diversimode et ad multa; iudicatur autem per rationem, in uno actu, aliquid appetendum secundum determinatas rationes et circumstantias.
Now it is clear that the active principle which is reason, cannot entirely overcome the appetitive power in one act: because the appetitive power is inclined variously, and to many things; while the reason judges in a single act, what should be willed in regard to various aspects and circumstances.
Unde ex hoc non totaliter vincitur appetitiva potentia, ut feratur in idem ut in pluribus, per modum naturae, quod pertinet ad habitum virtutis. Et ideo habitus virtutis non potest causari per unum actum, sed per multos.
Wherefore the appetitive power is not thereby entirely overcome, so as to be inclined like nature to the same thing, in the majority of cases; which inclination belongs to the habit of virtue. Therefore a habit of virtue cannot be caused by one act, but only by many.
In apprehensivis autem potentiis considerandum est quod duplex est passivum, unum quidem ipse intellectus possibilis; aliud autem intellectus quem vocat Aristoteles passivum, qui est ratio particularis, idest vis cogitativa cum memorativa et imaginativa.
But in the apprehensive powers, we must observe that there are two passive principles: one is the "possible" [See I, 79, 2 ad 2] intellect itself; the other is the intellect which Aristotle (De Anima iii, text. 20) calls "passive," and is the "particular reason," that is the cogitative power, with memory and imagination.
Respectu igitur primi passivi, potest esse aliquod activum quod uno actu totaliter vincit potentiam sui passivi, sicut una propositio per se nota convincit intellectum ad assentiendum firmiter conclusioni; quod quidem non facit propositio probabilis. Unde ex multis actibus rationis oportet causari habitum opinativum, etiam ex parte intellectus possibilis, habitum autem scientiae possibile est causari ex uno rationis actu, quantum ad intellectum possibilem.
With regard then to the former passive principle, it is possible for a certain active principle to entirely overcome, by one act, the power of its passive principle: thus one self-evident proposition convinces the intellect, so that it gives a firm assent to the conclusion, but a probable proposition cannot do this. Wherefore a habit of opinion needs to be caused by many acts of the reason, even on the part of the "possible" intellect: whereas a habit of science can be caused by a single act of the reason, so far as the "possible" intellect is concerned.
Sed quantum ad inferiores vires apprehensivas, necessarium est eosdem actus pluries reiterari, ut aliquid firmiter memoriae imprimatur. Unde philosophus, in libro de memoria et reminiscentia, dicit quod meditatio confirmat memoriam. Habitus autem corporales possibile est causari ex uno actu, si activum fuerit magnae virtutis, sicut quandoque medicina fortis statim inducit sanitatem.
But with regard to the lower apprehensive powers, the same acts need to be repeated many times for anything to be firmly impressed on the memory. And so the Philosopher says (De Memor. et Remin. 1) that "meditation strengthens memory." Bodily habits, however, can be caused by one act, if the active principle is of great power: sometimes, for instance, a strong dose of medicine restores health at once.
Philosophus dicit, in I Ethic., quod "una hirundo ver non facit, nec una dies, ita utique nec beatum nec felicem una dies, nec paucum tempus".
The Philosopher (Ethic. i, 7): "As neither does one swallow nor one day make spring: so neither does one day nor a short time make a man blessed and happy."
Sed "beatitudo est operatio secundum habitum perfectae virtutis", ut dicitur in I Ethic.
But "happiness is the activity of a habit of perfect excellence" (Ethic. i, 7,10,13).