As an Aristotelian virtue ethicist, Thomas accepts the essential outlines of Aristotle's ethics: eudaimonia, the doctrine of the mean, friendship. However, as a Christian writing many centuries after Aristotle, he has to relate Aristotle's work to the large body of ethical thought that had grown up since (deriving from Cicero, Seneca, Augustine, just to mention major influences on his ethical work) and also faces the problem that Aristotle's ethics in some ways seems inadequate to expounding Christian moral teaching. This will require him to step back and try to fit the whole framework of Aristotelian ethics into a larger framework that can make sense of its relationship with these other ethical strands. This will lead to a number of important modifications.
From Christian theology, Aquinas inherits a new definition of virtue, which he discusses in Summa Theologiae 2-1.55.4. According to this definition, virtue is
(1) a good quality of mind
(2) by which we live rightly
(3) which none can use badly
(4) which God works in us without us.
Thomas will accept this definition, although he thinks it needs to be understood a certain way. The bona qualitas mentis should be understood as a habit, the kind of second nature we saw in Aristotle's definition, and in particular as a rational habit. As with Aristotle, Aquinas takes virtue to be a habit concerned with acting, habitus operativus, and, of course, it has to be distinguished from vice (by it we live rightly) and from other habits besides vice (this is a habit none can use badly). Thus far, Thomas's interpretation of the definition treats this definition as covering the same ground, from a different direction, as Aristotle's definition of virtue, but the last element, which God works in us without us, is a new one, and Aquinas will handle it by holding that there is actually a distinction between two kinds of virtue. One, known to Aristotle, is acquired virtue or virtue that we gain by a process of habituation. The other, recognized only in Christian moral theology, is infused virtue or, in other words, a kind of virtue directly given by God (hence God works it in us) rather than by this natural process of habituation (hence God's giving it to us is 'without us'). The habit is given in a new and different way. In the Summa Theologiae, a work of theology, the virtues with which Aquinas is primarily concerned are infused virtues, to which this new definition applies. If we wanted to talk about all virtues whatsoever (acquired and infused), we would just focus on the first three elements.
The notion of infused virtues is ultimately rooted in the idea that faith, hope, and love, which are said to be given in Christian baptism, are virtues in a true and proper sense. These are called the theological virtues (Aquinas notes that they could also be called superhuman or divine virtues). A significant question, though, is whether there are any other infused virtues. Some Christian theologians (like John Duns Scotus) have held that there are no others. Thomas, however, has a very different view, and argues that Christian baptism confers not just the three theological virtues but also infused moral virtues. These infused moral virtues are necessary, he thinks, because the three theological virtues add a higher direction to human life than reason alone gives; that is to say, they contribute to the Christian's participation not just in human society (like ordinary acquired virtues) but in a supernatural society with God. Our acquired virtues, essential as they may be to good human society, are not adequate for this higher end that goes beyond our natural capacities, a higher happiness that Aquinas calls beatitude, and thus we need a new set of virtues. As he says in Summa Theologiae 2-1.63.4, drawing on Aristotle,
... the Philosopher says (Polit. iii, 3) that citizens have diverse virtues according as they are well directed to diverse forms of government. In the same way, too, those infused moral virtues, whereby men behave well in respect of their being "fellow-citizens with the saints, and of the household of God" (Ephesians 2:19), differ from the acquired virtues, whereby man behaves well in respect of human affairs.
Despite this difference, acquired moral virtues and infused moral virtues will tend to mirror each other, and thus what you learn about one can be used to understand the other, as long as you make allowance for their different ends and the different societies to which they contribute. Thus Thomas in his discussion of the infused virtues will draw heavily from philosophical discussions of acquired virtues.
This conception of the two societies will also make it possible for Aquinas to use Aristotle's discussions of friendship in an innovative way to understand the Christian virtue of charity. Thomas takes the theological virtues to establish a basis for friendship with God; the virtue of love or charity (caritas) is in fact nothing other than friendship with God. Friendship for Aristotle is not a virtue because it requires two people (although Thomas himself thinks Aristotle is a bit more ambiguous about this than he is often thought to be). You can have a virtue of friendliness, but this friendliness does not actually guarantee that the people to whom you are friendly are friends. However, charity as friendship with God is infused by God; therefore this no longer poses a problem. Thus charity is both a special kind of friendship and a virtue. Friendship therefore plays an even more important role in Thomas's approach than it does in Aristotle's, having all of the importance it has for Aristotle but one form of it also being the highest of all virtues.
In order to organize his discussion of the moral virtues, Thomas draws on the traditional list of the cardinal virtues. This is an old list -- a version of it is found in Plato, for instance -- but the name 'cardinal virtues' is fairly late, being due to St. Ambrose of Milan. The four cardinal virtues are prudence, justice, fortitude, and temperance. However, because of the age of the list, it has been used a number of different ways, so Thomas has to sort this out. One way we could take the list is as a description of the general conditions for virtue. In this sense, each one is like dimensions of the other virtues.
prudence: virtues insofar as they accomplish rational good.
justice: virtues insofar as they accomplish the good that is due and right in action
fortitude: virtues insofar as they strengthen the mind against the passions
temperance: virtues insofar as they restrain and suppress the passions
But more properly we could take the list to be a list of specific virtues of special importance. A way to think of this is that different virtues manifest the general conditions of virtue in more obvious or less obvious ways. So all virtues in some sense have a rational aspect, but some virtues are more obviously rational than others; and of these the virtue that is most important is that which actually concerns rational decision itself. Then we get:
prudence: the virtue of actual decision or command
justice: the virtue that concerns actions owed between equals
fortitude: the virtue that strengthens against fear of death
temperance: the virtue that represses the craving for physical pleasure
Of course, it's also the case that sometimes we speak more loosely, so that we use the word 'prudence' for any virtue that has an obvious rational component, etc. In this sense we are applying the term to a family of virtues.
Because of this messiness from long use, Thomas needs a way to sort out how different lists of virtues are related to the cardinal virtues. The way he does this, the method of parts, is remarkably comprehensive and flexible. The Latin word for 'part' could mean three different things: integral parts, subjective parts, and potential parts. By analogy these can be extended to virtue. As he says in Summa Theologiae 2-2.48.1:
Parts are of three kinds, namely, "integral," as wall, roof, and foundations are parts of a house; "subjective," as ox and lion are parts of animal; and "potential," as the nutritive and sensitive powers are parts of the soul. Accordingly, parts can be assigned to a virtue in three ways. First, in likeness to integral parts, so that the things which need to concur for the perfect act of a virtue, are called the parts of that virtue.... The subjective parts of a virtue are its various species.... The potential parts of a virtue are the virtues connected with it, which are directed to certain secondary acts or matters, not having, as it were, the whole power of the principal virtue.
Strictly speaking, virtues don't have integral parts, i.e., parts in our usual English sense of the word; virtues are unified things. However, the complete act of the virtue sometimes depends on other things, and these can be regarded as quasi-integral parts. So, for instance, prudence requires caution, understanding, willingness to learn, etc. Sometimes we give different names to one and the same virtue operating under different conditions. Thus chastity and sobriety are both temperance but with respect to different physical pleasures. They are subjective parts: you can 'divide' the virtue of temperance into these two parts, but each part is still fully the virtue of temperance.
Potential parts of a virtue are in many ways the most interesting. Some virtues are very like other virtues, but deviate from them in particular ways so that they are related but less central in some way; they are thus ancillary or annexed or secondary virtues associated with a principal virtue. Thus justice has a number of potential parts: virtues that are justice-like, that might even sometimes be called 'justice', but are more like satellite virtues in the justice family of virtues. For instance, justice is paying what you strictly owe to achieve an appropriate equality between equals; filial piety (pietas) is like justice in that it involves rendering to your parents what is due, but the debt is not a debt that can be paid so that you are now 'even' with your parents, who gave you life and raised you, while friendliness is like justice in that it concerns how you relate to another person, and could even be expressed in terms of rendering what you owe other people, but the 'owing' here is not a strict, definite debt that you really pay back, but more like an obligation to human beings generally. These are justice-like enough that you can talk about them in the same terms, and they are enough alike that you can see how, e.g., filial piety, while definitely a different virtue from justice, may facilitate being just.
By means of this classification, Aquinas is able to relate a wide variety of different discussions of virtues to each other in a consistent and unified way. If you find a virtue in a list, it is either a principal virtue or is related to a principal virtue in some way, either as a quasi-integral part, or as a subjective part, or as a potential part.
It is also useful to have a way of classifying vices. One could classify them according to the virtues they oppose, of course, but the result, while useful for understanding virtues, is unwieldy for the practice that would most benefit from a classification of vices, namely, self-examination. Vices, however, are difficult to put into a neat and tidy list, because they are legion -- the doctrine of the mean establishes that there are at least two for every acquired virtue -- and disunified -- unlike virtues, which are unified, vices oppose other vices. The traditional way around this is to take an indirect approach. Instead of trying to capture all the vices in a simple way, as with the cardinal virtues, focus on the thing that is most relevant for practice, which is the fact that some vices prepare the way for other vices, and make your list based on that. Some vices are 'gateway vices'; they mess with your head in such a way that if you get them, you have already started developing other vices. The usual metaphor for this, going back to St. Gregory the Great, is that of a queen vice and her seven generals, each coming at the head of the army. This metaphor is the source of the name of the list: the seven capital vices, from the Latin word 'caput', meaning 'chief' or 'head'. Pride, of course, is the queen, and the vices at the head of her seven armies are vainglory, envy, wrath, sloth, avarice, gluttony, and lust. The vices in their armies are called daughter vices; they don't have to originate in a capital vice, but they often do.
It's important to grasp that a vice is not on the list because it is among the worst vices. There are vices worse than any on the list of capital vices. For instance, the vice of odium (hatefulness/hatred) is a very terrible vice that is not a capital vice. Thomas calls it a terminal vice, because it's a vice so bad you can usually only get it in its complete form if you have a lot of other vices. It usually already requires a certain sort of wickedness to be able to do the actions that solidify into it. Capital vices, on the other hand, are initial vices. They all (1) are easy to get because they arise from common temptations and (2) make it so easy to get their associated daughter vices that if you are developing the capital vice you are probably also developing some of the daughter vices. And of course, the daughter vices often lead to other vices, even if not as virulently, in a cascade of moral deterioration, unless one deliberately works against them. Once a general breaches your wall, you have to fight the army that comes behind.
The list of the seven capital vices grew up over time from practical use in the practice of self-examination. However, Thomas thinks that the list can be justified more theoretically, as well. All moral temptation, and all moral error, branches off into two kinds: to treat bad as if it were good because it is associated with something that seems good and to treat good as if it were bad because it is associated with something that seems bad. The big categories of things that immediately seem good are those that pertain to soul, to body, and to human life insofar as it uses the external environment around it; and our assessment of what seems bad to us depends in great measure on how the goods involved are related to us. This helps us build an explanation for each of the seven capital vices based on the most powerful motivators in these areas.
Vices that treat bad as good
(1) due to association with the most strongly motivating good of the soul, our own excellence: vainglory
(2) due to association with the most strongly motivating goods of the body, physical pleasures
(a) connected to individual survival, i.e., food and drink: gluttony
(b) connected to survival of the human race, i.e., sex: lust
(3) due to association with the most strongly motivating external good, i.e., possession of what is useful for self-sufficiency: avarice
Vices that treat good as bad
(1) because of the most strongly deterring badness associated with ourselves, physical difficulty: sloth
(2) because of the most strongly deterring apparent badnesses associated with other people
(a) that their good seems to hurt us: wrath
(b) that their good makes us seem less excellent: envy
Together these vices capture the most common paths by which temptation arises for human beings in general. Individuals may be tempted in other directions, but these identify recurrent, widespread, powerful temptations. When we fall to temptations, we sin, that is to say, engage in an act associated with vice. Many sins build up to a vice. These sins can be of all sorts, but some sins are more typical of vices than others. For instance, you might kill someone out of greed, but this is not the usual kind of greed-associated action people are tempted to, and killing out of greed itself depends and is a sort of extension of one of these more typical actions (which is why we recognize as it as killing out of greed rather than something else). These more typical actions of the vices generally concern desires and the like that directly affect our choices; and these typical actions for the vices have come commonly to be known as the seven deadly sins. It is important to grasp that both vices and virtues can serve as the root for a very wide variety of actions; they are not confined to individual occurrences of typical acts but are capable of organizing entire areas of human life.
If we have some understanding of virtues and of vices, we still want to know what kinds of actions are appropriate to developing and maintaining virtues, and reducing or avoiding vices, in our own particular lives. All moral action, however, is situated action. You cannot adequately determine what is appropriate for you to do simply by looking at a general characterization of virtue and vice; that may give guidance, but you are not living life in general but a very particular life with very particular conditions. We live and act under different morally relevant conditions, and this has to be considered. Some of the conditions under which we labor are quite passing, and these are simply handled by prudence on a case-by-case basis. But some of our morally relevant conditions are fairly stable, and the most important of these are those that are most closely related to us as persons, that is to say, those that affect our general degree of freedom to act on our own or, on the other side, that involve serving others. This kind of condition St. Thomas calls a state of life (status vitae). It is your moral station, the position from which you act virtuously or not. Through experience with a given state of life, we come to recognize certain offices (officia) or duties that have to be performed on a regular basis in order to act virtuously in that state. Both states and offices differ from grade (gradus) or rank, which is something that, while sometimes morally relevant, we have only indirectly relative to the whole of society, rather than something pertaining to us ourselves. Likewise, we have to distinguish (because failing to do so is a common modern error) all of these from class, i.e., whether you are rich or poor; your station in life is not a matter of your relation to external possessions but of your situation insofar as you are a person capable of acting and serving.
Thomas, concerned primarily with infused virtues, naturally focuses on states of life pertaining to the broader supernatural society to which humans are introduced by the Church. He identifies several kinds of state, which are pretty clearly not intended to be exhaustive but just particularly important for life in the Church, e.g.,
(1) (what calls for) beginning, progressing, or completeness in virtue
(2) the episcopal state or prelature
(3) the religious state, such as with monks, nuns, and the like, and the secular state, such as parish priests and deacons
Moral stations in the Church all fall into two general categories, those devoted to the contemplative life and those devoted to the active life, and, of course, we can be in multiple states of life at once.
Even adding states and offices to our consideration, we do not have everything we need in order to live the moral life, because these are things pertaining to yourself alone, and Thomas Aquinas does not think human beings can be moral entirely on their own. We need assistance from outside ourselves, of which the two primary kinds are law and grace, to which we will turn in the next post.