Aquinas and Unity of Virtues

imagesThe problem of connection of virtues is about whether one can have a perfect virtue without having the other perfect virtues. Aquinas claims that, unlike imperfect virtues, the perfect virtues are connected, and one cannot have perfect virtues without the others. Furthermore, he argues that the relationship between moral virtues and prudence is a mutual entailment, i.e. one cannot have moral virtues without prudence or prudence without moral virtues. On the other hand, Abelard’ philosopher denies Aquinas’s claim that prudence is a moral virtue per se. Abelard’s philosopher argues that 1) prudence although necessary for moral virtues, it is not a virtue itself and 2) Prudence is the knowledge that makes a person able to distinguish between good and bad. As he puts it, “Certainly prudence is this knowledge of morals that is called, as a certain treatise on ethics transmits to us, the ‘science of good and evil things’—discerning goods or evils that in themselves are properly to be called good or evils” (DPC 265).[1] And 3) the good and bad both can have prudence. In fact, Abelard’s philosopher argues that virtues are connected, but to him, what connects virtues is an internal interdependency type of relationship between moral virtues. I found Aquinas’s second argument, presented in Summa Theologiae 1.56.1 R) more convincing than Abelard’s philosopher inconsistent argument about the relationship between prudence and moral virtues. I shall first sketch both philosophers’ arguments then explain why I think Aquinas makes a stronger case.

Before reformulating Aquinas argument for the mutual entailment of the moral virtues and prudence, highlighting some preliminary points are necessary in order to understand his argument better. For Aquinas a virtue, “disposes an agent to perform its proper operation or movement” ST IaIIae 49.1). On the other hand, prudence for Aquinas is the practical wisdom that enables one to choose a proper mean suitable for a proper end. As he puts it, prudence is a “certain rectitude of discretion in any actions or matters whatever” (ST IaIIae 61.4). It is necessary to know that prudence for Aquinas is not same as cleverness. The former is not compatible with moral virtues while the latter is compatible with moral virtues. For instance, one may plan a murder cleverly; however, this is not an act of prudence for Aquinas. An evil person can be clever but not prudent. However, it seems that this the point that Abelard’s philosopher and Aquinas differ, for Abelard’s philosopher believes that both the good and bad can have prudence.

Aquinas presents a bi-conditional argument for mutual entailment of moral virtues and prudence. For him, there are two conditions for any morally significant action. The first is general moral principles that govern actions, and the second is applying those general principles in a particular circumstance.

Aquinas’s argument for mutual entailment of prudence and moral virtues can be formulated as follows:

  • To reach an end, it is necessary to choose means that are suitable to the end.
  • Moral virtues set proper ends, and dispose an agent to act virtuously.
  • Prudence is the practical wisdom to choose means suitable to the ends.
  • Prudence does not determine the end (moral virtues).
  • Therefore, there is no moral virtue without prudence.
  • Therefore there is no prudence without moral virtues.

To Aquinas, perfect virtues are justice, prudence, courage, and moderation. Unlike imperfect moral virtues, perfect moral virtues are connected. Aquinas defines a perfect moral virtue as, “a habit that inclines one to perform good deed well” (ST 1.65.1 R). However, inclination by itself is not sufficient for making the right choice. As he puts it, “For it is proper to moral virtue to make the right choice, since it is an elective disposition (habitus). But an inclination for the proper end, directed by the habit of moral virtue, does not suffice for right choice” (St 1.65.1 R. I.51-57). Moral virtues set proper ends; however, a proper end or an inclination for seeking proper ends is not sufficient for choosing proper means. Therefore, one cannot accomplish those ends without prudence. A physician may know all of the theoretical knowledge and the first principles of his science; however, if he lacks prudence, he will not be able to apply his knowledge properly on a particular patient and disease. By the same token, a person needs prudence to know how to do his/her moral virtues well. Another example that reveals the dependency of moral virtues on prudence is that if a just person lacks prudence, this deficiency destroys his/her justice. The classical example is the imprudent just person who wants to do his/her moral duty and returns someone’s sword when the owner is drunk and angry. In this case, the lack of prudence destroys his justice, because an angry drunk who owns a sword might harm innocent people, and it is not compatible with justice. Therefore, there is no moral virtue without prudence.

On the other hand, the second part of the bi-conditional argues that there is no prudence without moral virtues. Prudence does not establish the end. Prudence is a practical knowledge of how to apply universal principles in a particular situation; however, it establishing the end requires the knowledge of universals. As he puts it, “For [prudence] is right reason concerning what is to be done, which proceeds as from [the first] principles from the goals (fines) [we set about] what can be done, the goals to which a person is rightly related by the moral virtues” (ST 1.56.1 R, I 57-60). He maintains that finding the means to achieve wicked end causes by lack of prudence. Therefore, he concludes, there is no prudence without moral virtues.

Abelard’s philosopher views prudence as the mother or the origin of moral virtue; however, unlike Aquinas, he claims that it is compatible with evil ends. In other words, for Aquinas, prudence is not compatible with cleverness whereas for Abelard’s philosopher a clever person can be prudent too. For Abelard’s philosopher, prudence is necessary for having moral virtues. However, the good and the evil both might have prudence (DPC 258). If, as Abelard’s philosopher understands, prudence is “science of good and evil” (DPC 256), then the good and evil can have this knowledge. Furthermore, this science per se does not make a person good or bad. For Abelard’s philosopher, in addition to the science of good and evil, 1) good intention and 2) strength of the will/mind are necessary for moral actions. He states, “Therefore, we call both of these a kind of firmness and steadiness of the mind whereby we are enabled to carry out what we want through justice. Their contraries are indeed rightly called a kind of mental weakness or inabilities to resist vices (267). He defines virtue as “the mind’s best habit” (DPC 254) that is attainable through repetitive practices so that a virtuous person would act virtuously against all the obstacles and temptations (DPC 266). A vice, on the contrary, is the opposite of virtue, so the mind’s worse habit” that makes a person act viciously. It seems that Abelard’s philosopher would reject the second half of Aquinas bi-conditional, i.e., no prudence without moral virtues. Therefore, unlike Aquinas the notion of a wicked prudent person is not an inconsistent notion, to Abelard’s philosopher.

I tend to agree with Aquinas on his account that there is no prudence without moral virtues. One may agree with Abelard’s philosopher that prudence is not a moral virtue per se; however, he does not make a convincing case when he argues that prudence is compatible with moral vices. In fact, he reduces the scope of prudence to merely a “science of good and evil,” which lacks to determine right choices. Abelard’s philosopher on the one hand believes that prudence is the mother or origin of moral virtues; on the other hand, he maintains that prudence can be shared by the good and the bad equally. I think Aquinas is right to reject the latter claim, since 1) prudence is not merely a “science of good and evil” and 2) it is to know how to act virtuously in a particular situation. Therefore, I think Aquinas make a stronger case.


[1] In 256, Abelard’s philosopher mentions “some people” who calls “prudence’s discernment the mother or origin of the virtues rather than itself a virtue.” It seems that it is also Abelard’s view too. In his Ethics 227, he reiterates the same point. He states, “Prudence—that is, the discrimination of good and evil—is the mother of virtues rather that itself a virtue.” Regardless, to say that Abelard’s philosopher holds the view that prudence is necessary for moral virtue is a matter of interpretation of his characterization of prudence as “mother of virtues.” If an offspring cannot come into existence without a mother, then having a mother is a necessary condition for birth; however, it is not a sufficient condition, since birth requires a father too. If this is the analogy the Abelard’s philosopher has in mind, then his position on the insufficiency of prudence is not fundamentally different from Aquinas. Since Aquinas also maintains that there is no moral virtue without prudence. However, as we will see Abelard’s philosopher reject the second part of the bi-conditional, i.e., no prudence without moral virtues.


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