Along with consequentialism and other so-called "teleological" theories of morality, "proportionalism" has the distinction of being singled out for censure by a papal encyclical (see Veritatis Splendor 79). Whether it deserves this opprobrium is something its advocates vigorously dispute. The late Richard McCormick, S.J., perhaps the most articulate of English-speaking defenders of the approach, disdained to find in Veritatis Splendor's description of proportionalism anything resembling the method he and others had been championing in their post-Conciliar efforts to revise Catholic moral theology.
At issue is whether there are certain kinds of acts, call them "moral abominations," that can be defined ahead of time, i.e., independent of intention and circumstance, as unqualifiedly wicked—intrinsice inhonestum in the argot of the tradition. Proportionalists are often taken as denying the existence of such acts, and are thus decried as unable to account for some of our most dearly and deeply held moral intuitions, for example, our repugnance at the judicial execution of the innocent, regardless of the greater good it might occasionally serve ("Better one man perish . . ." etc.).
For his part, at least, McCormick never denied the existence of such acts, only that one could define them without reference to the intention of the acting person. On a very common proportionalist view of practical reasoning, every human choice involves the manufacture of some disvalue, some evil, even if only in opportunity costs ("the path not taken"). Accordingly, the objectively right thing to do in any situation will be determined by seeking the proper "proportion" between the good one wants and the evil one prospectively creates or allows. Only when the intended good outweighs the evil, or at the very least is not undermined by it, is an act morally permissible. For example, artificial methods of birth control, though introducing a disvalue in the "conjugal act" by rendering it non-procreative, may nevertheless be justified when their use serves a higher, more important good (e.g., marital unity, family welfare). Judicial execution of the innocent is excluded because, all other things being equal, one undermines the value of justice in the very act of administering it. In sum, for proportionalists, only those acts in which a disproportionate evil is intended-e.g., blasphemy, leading others into sin-are inherently wicked.
Whether this account of practical reason makes sense is, of course, open to question; at the same time, however, it is important to observe, as Christopher Kaczor does in Proportionalism and the Natural Law Tradition, that the debate between proportionalism and its critics is not between tradition-bashing radicals, on the one side, and orthodox defenders of the faith on the other, but a debate within a tradition in which all sides claim to be extending the best insights of the "natural law" framework of Catholic moral theology, and in particular those of St. Thomas Aquinas. Hence, those tempted to dismiss proportionalism simply because it has been the target of magisterial ire would do well to read Kaczor.
Kaczor begins by making the case for proportionalism "as understood by its advocates," which is no mean feat, since its advocates are a diverse lot with some important differences among them. However, Kaczor is certainly right to summarize proportionalists as engaged in something like a house-cleaning operation within the Catholic moral tradition, a project whose basic aim is to make that tradition more consistent, principally by translating the classical prohibitions of intrinsically evil acts into teleologically-grounded "virtually exceptionless" norms, as in the examples above. If there is a "general maxim" underlying the tradition in this regard it is what McCormick refers to as the indisputable principle that we always avoid the greater evil.
That many proportionalists see these moves as a "rational correction and improvement" of the tradition owes more to the fact that the "tradition" in question is that of the manuals of moral theology, the genre in which moral theology was practiced from roughly Trent to Vatican II. In an extremely illuminating chapter ("How Double-Effect Reasoning Became Proportionalism") Kaczor provides an account of proportionalism that emphasizes its (backhanded) indebtedness to the manuals, which were themselves significant departures from the assumptions and methods of Aquinas. Here then is the central—and quite powerful—claim of Kaczor's work: If proportionalism is persuasive as a moral theory, it is because it rests upon the correction of an already seriously flawed predecessor theory (that embodied in the moral manuals), which by the seventeenth-century had largely abandoned the achievements of the Summa Theologiae. "Proportionalism" takes its name from the last of the four conditions of so-called "Double Effect Reasoning" (DER), which has its origins in Aquinas's discussion of self-defense (ST II-II, 64, 7). There, Aquinas argues that the amount of force used to repel an aggressor must be proportioned to the end of self-defense. Violence beyond that would morally vitiate the act by disclosing a will bent on the harm or death of the aggressor, which Aquinas strictly rules out as contrary to virtue. By the time of the influential manualist Jean Pierre Gury (1801-1866), DER has emerged as a discrete "principle" within the tradition, though "proportion" is now parsed in terms of the good and evil effects produced by a single act, not between an act and its effect. With the emergence of "proportionalism" in the 1960s, DER becomes absolutely central. There, the distinction between pre-moral goods (values) and evils (disvalues) completes the reduction of DER to its fourth condition: "proportionate reason." Every moral act occurs to some extent in a conflict situation between desired values and undesirable disvalues. Right actions will thus be those that aim at the greater balance of value over disvalue.
According to Kaczor, the misstep taken by the manualists, upon which proportionalism builds, is the abandonment of Aquinas' (and before him Aristotle's) understanding of human action. In brief, proportionalism tends to lose the distinction between art and prudence, between forms of reason (and standards of evaluation) proper to craft, factio, techne, on the one hand, and human action as measured by virtue, arete, on the other. "It is surely unsound to believe that the better the craftsman the better the person morally. The good craftsman may be a good person, but the good craftsman may also be an evil person" (134-35).
In the end, Kaczor's argument is that a careful recovery of Aquinas' account of human action (I-II 1-21) successfully resolves those problems within proportionalist theory that proportionalism itself is unable to remedy, thereby establishing itself as the rationally superior version of a "natural law" approach to moral reason. In doing so Kaczor has given us a model of how moral argument can go within the Catholic tradition.