Since the first principle of morality is at once so important and so difficult to grasp, further reflection might be helpful to clarify its precise meaning and so to help make its truth comprehensible. To some extent this clarification will come about in later discussions, as the principle is shaped into general modes of responsibility and specified by the human condition understood in the light of faith. However, even at the present level of abstractness, some additional explanation of the first principle is possible.

Any ethical theory based upon the ordering of human actions to human fulfillment must account for the fact that not every choice is morally evil, yet every choice responds to the appeal of the human goods promised by one possible course of action and leaves unanswered the appeal of the equally basic and incommensurable goods promised by one or more other courses of action. That each of these goods is to be realized and protected is a starting point for deliberation about possibilities which would realize or protect it. Such a starting point is a (premoral) principle of practical reasoning. Corresponding to the whole set of basic human goods is the whole set of principles of practical reasoning.

The whole set of principles directs that all the goods be realized and protected. But even morally evil acts depend upon and respond to some of these principles. Therefore, none of the principles of practical reasoning is a moral norm merely by being a principle of practical reasoning. That human life is a good to be protected, for example, does not by itself dictate that killing is always wrong.

The distinction between moral good and evil is a distinction between ways in which proposed courses of action are related to the whole set of principles of practical thinking. Some proposals comport well with all of the human goods. Others comport well with some of the principles of practical thinking—those which direct action to the goods promised by these proposals—but are inconsistent with or inadequately responsive to one or more others. It is morally good to adopt proposals of the former sort and morally bad to adopt proposals of the latter sort.

One about to choose in a morally right way respects equally all of the basic human goods and listens equally to all of the appeals they make through the principles of practical thinking. Because of the incompatibility of concrete possibilities—one cannot do everything at once—choice is necessary. No single good, nothing promised by any single possible course of action, exhausts human possibilities and realizes integral human fulfillment. But just as two propositions which have no common terms cannot be inconsistent with each other, so any proposed course of action is consistent with those principles of practical thinking to which it is merely irrelevant. Moreover, one who chooses cannot be inadequately responsive to a principle of practical thinking if the principle in question has played no role whatsoever in the deliberation leading to that choice.

Thus, one can choose in a morally upright way. One can choose one possibility which promises certain goods and is irrelevant to other goods promised by an alternative, without violating the practical principle which directs action to these other goods. One does not adopt a restrictive standard of human fulfillment. One’s understanding of all the human goods, one’s appreciation of the special contributions they can make to integral human fulfillment, remains the same after the choice as before.

One about to choose in a morally wrong way does not respect and respond equally to all of the basic human goods, does not listen equally to all of the appeals they make through the principles of practical thinking. The proposal he or she is about to adopt involves detriment to some human good, or at least it involves slighting some good. One is tempted to accept this detriment to or slighting of a good for the sake of another good which will thereby be possible. Such a proposed course of action is responsive to at least one principle of practical thinking, and it might be irrelevant to—and so consistent with—some others. But it is both relevant to and inconsistent with (or, at least, inadequately responsive to) the principle which directs to the good with which the choice comports less well. Yet the goods represented by these different principles are equally basic and equally essential to the ideal of integral human fulfillment.

Thus, one can choose in a morally wrong way. One is wholly or partly voluntarily unresponsive to the appeal of some of the basic human goods. In making such a wrong choice—a procedure which might be called “exclusivistic choice”—one’s understanding of the various goods is itself affected. The good which is violated or downrated is no longer considered equally basic and incommensurable with the good which is preferred. The preferred good is considered a “greater good” while the other becomes a “lesser good.” The choice, which is partly irrational insofar as it is inadequately responsive to some principle of practical thinking, is rationalized by reappraising the value of the good one has rejected or whose appeal one has partly ignored.

Although the fair treatment of persons is itself a question within morality, one can understand the preceding explanation by analogy with fairness and unfairness. The principles of practical reason which are in play during deliberation are like the appeals for consideration made by a number of different persons. When one is confronted with many different and incompatible requests, one cannot satisfy all of them. One must choose. An upright person will be impartial in making this choice. One appeal will not be preferred and another set aside out of motives which have nothing to do with the content of the various appeals. If one were to do this, one would have to ignore or even deny part of the intrinsic force of the appeal one rejected. After making such a choice, one could not continue to regard all of the persons involved as equal. One would have to pretend the person one treated unfairly was of less worth, thus to justify the unfair treatment. In making immoral choices, we deal in a similar way with the various basic human goods and the principles of practical reason which represent them in deliberation.