Whether some concupiscences are natural, and some not natural?
Objection 1: It would seem that concupiscences are not divided into those which are natural and those which are not. For concupiscence belongs to the animal appetite, as stated above (A[1], ad 3). But the natural appetite is contrasted with the animal appetite. Therefore no concupiscence is natural.
Objection 2: Further, material differences makes no difference of species, but only numerical difference; a difference which is outside the purview of science. But if some concupiscences are natural, and some not, they differ only in respect of their objects; which amounts to a material difference, which is one of number only. Therefore concupiscences should not be divided into those that are natural and those that are not.
Objection 3: Further, reason is contrasted with nature, as stated in Phys. ii, 5. If therefore in man there is a concupiscence which is not natural, it must needs be rational. But this is impossible: because, since concupiscence is a passion, it belongs to the sensitive appetite, and not to the will, which is the rational appetite. Therefore there are no concupiscences which are not natural.
On the contrary, The Philosopher (Ethic. iii, 11 and Rhetor. i, 11) distinguishes natural concupiscences from those that are not natural.
I answer that, As stated above (A[1]), concupiscence is the craving for pleasurable good. Now a thing is pleasurable in two ways. First, because it is suitable to the nature of the animal; for example, food, drink, and the like: and concupiscence of such pleasurable things is said to be natural. Secondly, a thing is pleasurable because it is apprehended as suitable to the animal: as when one apprehends something as good and suitable, and consequently takes pleasure in it: and concupiscence of such pleasurable things is said to be not natural, and is more wont to be called "cupidity."
Accordingly concupiscences of the first kind, or natural concupiscences, are common to men and other animals: because to both is there something suitable and pleasurable according to nature: and in these all men agree; wherefore the Philosopher (Ethic. iii, 11) calls them "common" and "necessary." But concupiscences of the second kind are proper to men, to whom it is proper to devise something as good and suitable, beyond that which nature requires. Hence the Philosopher says (Rhet. i, 11) that the former concupiscences are "irrational," but the latter, "rational." And because different men reason differently, therefore the latter are also called (Ethic. iii, 11) "peculiar and acquired," i.e. in addition to those that are natural.
Reply to Objection 1: The same thing that is the object of the natural appetite, may be the object of the animal appetite, once it is apprehended. And in this way there may be an animal concupiscence of food, drink, and the like, which are objects of the natural appetite.
Reply to Objection 2: The difference between those concupiscences that are natural and those that are not, is not merely a material difference; it is also, in a way, formal, in so far as it arises from a difference in the active object. Now the object of the appetite is the apprehended good. Hence diversity of the active object follows from diversity of apprehension: according as a thing is apprehended as suitable, either by absolute apprehension, whence arise natural concupiscences, which the Philosopher calls "irrational" (Rhet. i, 11); or by apprehension together with deliberation, whence arise those concupiscences that are not natural, and which for this very reason the Philosopher calls "rational" (Rhet. i, 11).
Reply to Objection 3: Man has not only universal reason, pertaining to the intellectual faculty; but also particular reason pertaining to the sensitive faculty, as stated in the FP, Q[78], A[4]; FP, Q[81], A[3]: so that even rational concupiscence may pertain to the sensitive appetite. Moreover the sensitive appetite can be moved by the universal reason also, through the medium of the particular imagination.
Whether concupiscence is infinite?
Objection 1: It would seem that concupiscence is not infinite. For the object of concupiscence is good, which has the aspect of an end. But where there is infinity there is no end (Metaph. ii, 2). Therefore concupiscence cannot be infinite.
Objection 2: Further, concupiscence is of the fitting good, since it proceeds from love. But the infinite is without proportion, and therefore unfitting. Therefore concupiscence cannot be infinite.
Objection 3: Further, there is no passing through infinite things: and thus there is no reaching an ultimate term in them. But the subject of concupiscence is not delighted until he attain the ultimate term. Therefore, if concupiscence were infinite, no delight would ever ensue.
On the contrary, The Philosopher says (Polit. i, 3) that "since concupiscence is infinite, men desire an infinite number of things."
I answer that, As stated above (A[3]), concupiscence is twofold; one is natural, the other is not natural. Natural concupiscence cannot be actually infinite: because it is of that which nature requires; and nature ever tends to something finite and fixed. Hence man never desires infinite meat, or infinite drink. But just as in nature there is potential successive infinity, so can this kind of concupiscence be infinite successively; so that, for instance, after getting food, a man may desire food yet again; and so of anything else that nature requires: because these bodily goods, when obtained, do not last for ever, but fail. Hence Our Lord said to the woman of Samaria ( Jn. 4:13 ): "Whosever drinketh of this water, shall thirst again."
But non-natural concupiscence is altogether infinite. Because, as stated above (A[3]), it follows from the reason, and it belongs to the reason to proceed to infinity. Hence he that desires riches, may desire to be rich, not up to a certain limit, but to be simply as rich as possible.
Another reason may be assigned, according to the Philosopher (Polit. i, 3), why a certain concupiscence is finite, and another infinite. Because concupiscence of the end is always infinite: since the end is desired for its own sake, e.g. health: and thus greater health is more desired, and so on to infinity; just as, if a white thing of itself dilates the sight, that which is more white dilates yet more. On the other hand, concupiscence of the means is not infinite, because the concupiscence of the means is in suitable proportion to the end. Consequently those who place their end in riches have an infinite concupiscence of riches; whereas those who desire riches, on account of the necessities of life, desire a finite measure of riches, sufficient for the necessities of life, as the Philosopher says (Polit. i, 3). The same applies to the concupiscence of any other things.
Reply to Objection 1: Every object of concupiscence is taken as something finite: either because it is finite in reality, as being once actually desired; or because it is finite as apprehended. For it cannot be apprehended as infinite, since the infinite is that "from which, however much we may take, there always remains something to be taken" (Phys. iii, 6).
Reply to Objection 2: The reason is possessed of infinite power, in a certain sense, in so far as it can consider a thing infinitely, as appears in the addition of numbers and lines. Consequently, the infinite, taken in a certain way, is proportionate to reason. In fact the universal which the reason apprehends, is infinite in a sense, inasmuch as it contains potentially an infinite number of singulars.
Reply to Objection 3: In order that a man be delighted, there is no need for him to realize all that he desires: for he delights in the realization of each object of his concupiscence.