There is a tendency, especially when discussing questions of law and politics in the classical, Catholic tradition, to overlook the meaning of the terms and concepts used by Aquinas and others in their expressions of that tradition. But Aquinas reminds us: “parvus error in principio magnus est in fine”—“a little error in the beginning is a big one in the end” (De ente et essentia, Prooemium). It is therefore necessary to keep these definitions in mind. An exploration of the consequences of a couple of central concepts—happiness and the common good—will suffice for a demonstration.

We know that in practical matters the first principle is the last end (ST IaIIae q.90 a.2 co.). The last end of human life is bliss or happiness (ST IaIIae q.2 a.7 co.). Aquinas tells us that law, therefore, must regard happiness and indeed, because man is a political animal, not just the happiness of an individual man but the happiness of the community (ST IaIIae q.90 a.2 co.). Aristotle tells us much the same thing when he treats justice in the Nicomachean Ethics: a just law produces and preserves happiness for the community (NE 5.1, 1129b12-27). And this happiness is the common good (In V Ethic. L.2, nos. 902–903),

So far, there is nothing too controversial in saying that laws must be framed to produce and preserve happiness for the community, which is the common good. A problem inevitably arises when the terms are used without any understanding of their meaning. It is all too common to hear the common good—or happiness—used mostly to mystify discussions or to smuggle in specific ideas, which have very little to do with the concepts as they are used. Insistence upon clear understandings of the concepts involved leads to clear understandings of the consequences of the claims made.

Let us follow its trail for a while and see where we wind up. Happiness, which is the same thing as the common good, has a concrete meaning. If the political community—if, for example, the state—is to secure and preserve happiness, then it is necessary to understand happiness. The first principle in practical matters is the last end (ST IaIIae q.90 a.2 co.). It may be suggested that happiness consists, for example, in a particular arrangement of political and economic conditions that allow for citizens to do or not do this or that thing. Indeed, even in Catholic discourse, one might hear temporal happiness described in such terms, with the suggestion that eternal happiness is added to that in some way.

Yet this is a serious error. For one thing, when one makes political prudence or science the highest wisdom, one necessarily supposes that man is the best thing in the universe, as Aristotle tells us (NE 6.7, 1141a20). Man is however not the most excellent thing in the world (In VI Ethic. L.6, no. 1186). Another consequence, if one holds that man is the most excellent thing in the universe—and, therefore, that political science is the most excellent—would be to make actually practical rule impossible. Charles de Koninck, in his Principle of the New Order, demonstrates that practical reason directs to an end in accordance with right reason. This requires one to know the end. To reject the primacy of the speculative is to knock the legs out from underneath this process: without speculative reason one cannot know the final end—which is the first principle. Practical rule dissolves into mere will and chance.

The speculative intellect is important not merely for making practical rule possible. In the classical account, it is the proper end of law and the essence common good. Aristotle tells us that the most excellent virtue—complete happiness—is contemplative (NE 10.7, 1177a12). That is to say, for Aristotle, to contemplate what is true is the best part of man. And the contemplative life is the perfectly happy life. Aquinas explains that the contemplation of truth consists both in discovering the truth and in reflecting on truth already discovered (In X Ethic. L.10, no. 2092). However, reflecting on truth already discovered is more perfect than the investigations leading to the discovery of truth. The perfectly happy life, therefore, comes from contemplation by reason perfected by the intellectual virtue of truth.

Aristotle and Aquinas alike extol the superiority of the contemplative life. Aquinas tells us that “vita contemplativa non est proprie humana, sed superhumana”—“the contemplative life is not properly human, but superhuman” (QD de virt. card. a.1 co.). However, “vita […] voluptuosa, quae inhaeret sensibilibus bonis, non est humana, sed bestialis”—the life of pleasure […] by which one adheres to sensible goods, is not human but bestial” (ibid.). Human life is the active life according to the moral virtues (ibid.). But it must be remembered that “vita activa, in qua perficiuntur morales, est ut ostium ad contemplativam”—“the active life, which is perfected by the moral virtues, is as a door to the contemplative life” (QD de virt. in communi a.13 ad 24). In other words, the contemplative is the best part of man, toward which the active life is ordered (cf. Metaphysics A, c.2, 982b5; In I De Anima c.1). Aquinas goes so far as to hold that to take pleasure in created things, as opposed to the permanent things that offer pleasure in the contemplative life, is to incur an impurity of affection (In X Ethic. L.10, no. 2091).

However, the centrality of the contemplative life goes well beyond being superhuman and the true end of the active life, perfected by the moral virtues. Aquinas teaches us that the maximum in any genus is the cause of all in that genus (ST Ia q.2 a.3 co.). He gives the example of heat: fire, the maximum heat, is the cause of all hot things. This principle returns in an unexpected place. In the so-called treatise on law, Aquinas tells us that in every genus, that which belongs to it chiefly is the principle of the others and the other things in that genus are subordinated to that thing (ST IaIIae q.90 a.2 co.). Once again, Aquinas uses the example of heat: fire is chief among hot things is the cause of heat in mixed bodies, which may be said to be hot insofar as they have a share in fire. It may therefore be said that the happiness of the contemplative life is the cause and principle of the happiness of the active life.

Therefore, the most just laws, which secure the greatest happiness for the political community, which have the greatest share of the common good, are laws producing and preserving the contemplative life. The law must lead the citizens of the political community to virtue (ST IaIIae q.95 a.1 co.). But the highest virtue is the virtue of the contemplative life. To the extent that the law fosters and promotes the virtues of the active life, it must be remembered that the active life is as a door to the contemplative life (QD de virt. in communi a.13 ad 24). The lawgiver must therefore have first and foremost in mind the virtues of the contemplative life: in practical matters the first principle is the last end. And the lawgiver must have in mind the fact the happiness of the contemplative life is the cause and principle of the happiness of the active life, even if the happiness of the active life involves some impurity of affection (In X Ethic. L.10, no. 2091).

One could go follow this trail a while longer and come to still more interesting and surprising sights, but the point is clear enough. Concepts like “happiness” and “the common good” have meanings in the classical tradition, and these meanings have consequences. When one attempts to define these terms in a wholly materialistic sense or, worse, to pretend that they have no fixed meanings, one reaches toward the formlessness of modernity. This is a terrible thing to do, reducing practical reason itself to chance, and it is still more terrible to do so unwittingly.