Concupiscentia est passio differens specie et ab amore et a delectatione quia ipsum delectabile secundum sensum, inquantum appetitum sibi adaptat quodammodo et conformat, causat amorem; inquantum vero absens attrahit ad seipsum, causat concupiscentiam; inquantum vero praesens quietat in seipso, causat delectationem.
Desire is a passion differing in species from both love and delight because the [object] itself delectable to sense causes love, inasmuch as, in a certain way, it attunes and conforms the appetite to itself; it causes desire, inasmuch as, when absent, it draws [the concupiscible faculty] to itself; and it causes delight, inasmuch as, when present, it makes [the concupiscible faculty] to find rest in itself.
Est autem alia ratio virtutis motivae ipsius finis vel boni, secundum quod est realiter praesens, et secundum quod est absens, nam secundum quod est praesens, facit in seipso quiescere; secundum autem quod est absens, facit ad seipsum moveri.
Now the formal aspect of the motive power of the end (i.e., of the good), differs according as it is really present, or absent, because, according as it is present, it causes [the concupiscible faculty] to find rest in it; whereas, according as it is absent, it causes [the concupiscible faculty] to be moved towards it.
Bonum delectabile non est absolute obiectum concupiscentiae, sed sub ratione absentis, sicut et sensibile sub ratione praeteriti, est obiectum memoriae. Huiusmodi enim particulares conditiones diversificant speciem passionum, vel etiam potentiarum sensitivae partis, quae respicit particularia.
The delectable good is the object of [the passion of] desire, not absolutely, but considered under the formal aspect of absence, just as the sensible, considered under the formal aspect of the past, is the object of memory. For these particular conditions diversify the species of passions, and even of the powers of the sensitive part, which regards particular things.