Summa Theologiae Moralis, vol. I: De Principiis

S. Th. I-II, q. 6, a. 7; q. 73, a. 6; q. 77, a. 5 et 7; q. 78, a. 2 et 4

76. Concupiscence: 1° in the broadest sense it is either a) habitual disorder, i.e., the privation of rightness left by original sin in the sensitive appetite, especially when it tends toward a sensible good, and consequently in reason and will; or b) any passion or movement of the appetite that is disordered, preceding deliberation, especially when it tends toward evil or rises against reason (the first-first movement); 2° in the strictest sense it is a special passion whereby the concupiscible appetite tends toward an absent, delightful sensible good, and is opposed to fear, which is the movement of the appetite fleeing evil; 3° in a less strict sense, here it is taken not indeed for every passion, but for any affection or movement of the sensitive appetite or will tending toward a delightful good to pursue it¹.

In terms of the act of deliberate will, concupiscence is antecedent, which (in the order of causality) precedes the free consent of the will and causes it: then something is done from concupiscence, as when, upon seeing a beautiful woman, lust draws the will to take delight in her;— and consequent, which (in the order of causality) follows the free consent of the will and proceeds from it, as if, willing to sin with a woman, one excites concupiscence to perpetrate the sin: then something is done with concupiscence. It is evident that consequent concupiscence, since it follows upon the voluntary, in no way impedes it nor causes the involuntary, but is only a sign and effect of the voluntary. The question, therefore, concerns only antecedent concupiscence, namely how it stands with respect to the voluntary and the involuntary.

77. Principle I. Antecedent concupiscence causes the voluntary rather than the involuntary. — For something is called voluntary from the fact that the will is borne toward it. But through concupiscence the will is inclined to will that which it desires. Therefore concupiscence does more to make something voluntary than involuntary.

Therefore, to distinguish it from fear, concupiscence of itself never renders an act involuntary, either simply or in a qualified sense, because in one who acts from fear there remains a prior contrary will regarding what he does, but in one who acts from concupiscence there does not remain a prior will that repudiated what he desires, and therefore the one desiring acts against what he willed, while the one fearing acts against what he even now wills in itself. Concupiscence, however, does render an act involuntary accidentally when some evil is joined to the object that is desired, e.g., when a lustful man is at the same time avaricious and wills fornication, for the sake of procuring which he must pay out money.

78. Principle II. Antecedent concupiscence increases the voluntary, diminishes the free voluntary; whence what is done from concupiscence is more voluntary, less free². — For such concupiscence: 1° Always increases the voluntary improperly so called, because it itself, as an indeliberate movement of appetite, is in this way voluntary by its very nature.

2° Generally it increases the voluntary act properly so called as to the inclination or propensity, because our will is borne more toward the object we covet when the intellect proposes it as more covetable and to be pursued with greater efficacy; — yet it diminishes it as to the indifference of judgment and consequently as to deliberation. For it causes the intellect to perceive less the aspect of evil in the object and to propose it as more lovable; whence it also diminishes the free act, and consequently the goodness of the act and the sin.

3° Sometimes, if it is very vehement, it removes knowledge and deliberation and the use of reason, and hence the voluntary properly so called and the free; yet it does not make it involuntary: for in one who does not use reason, neither is it voluntary properly nor involuntary.

79. Observation.—Consequent concupiscence in no way diminishes the voluntary act properly so called, nor the free act, nor consequently goodness or sin, because it is itself an effect of the free will. Hence what is done with concupiscence is neither less voluntary nor less free. It can, however, diminish deliberation and freedom with respect to the act following from it; but with respect to that act, it is antecedent.