1. According to this view, the principles of our judgments of conscience are arbitrary demands made upon us by God. They might, for instance, be rules invented by God simply to test our obedience. If so, any judgment as to what is right could be reversed if God changed the rules. In this view, moral principles are not truths but commands.13 They do not express an intrinsic relationship between what is required and what is humanly fulfilling; fulfillment, rather, is a sort of prize awarded for passing a test which is otherwise unrelated to the prize.
2. This view, too, has a certain plausibility. We owe our existence and everything else to God—we are entirely dependent on his choice. Obedience to him thus seems inescapably necessary. Moreover, since we are his children, obedience seems altogether right. The view that moral principles are established by God’s arbitrary choice seems to fit these facts. Furthermore, it is more acceptable to a Christian than any of the views examined up to now. Thus, in the absence of a better account of normative principles, it appeals to a believer.
3. Still, this view must also be rejected. It is inconsistent with the truth of faith that God directs all things wisely and lovingly, not arbitrarily and despotically. The normative force of his commands cannot follow from the mere fact that he commands, any more than from the fact that we choose (see Dt 4.5–8). God’s will ought of course to be followed, but faith provides a cogent reason for doing so: that he is leading and guiding us toward our true good (see Ps 23).14
4. God’s will is not some sort of irrational force. By choice, he freely creates and redeems all things according to a wise plan. His wisdom settles what is good and bad for us and all creatures. By wisdom God makes us what we are and thus determines the true requirements for our fulfillment (see Gn 1.26–30; 2.18–24; Wis 7.21–8.1; DS 3002–3/1783–84; see S.t., 1–2, q. 71, a. 2, ad 4; q. 91, a. 2; q. 93, aa. 1–2; q. 100, a. 8). He does not make things right and wrong by an additional, arbitrary choice.
5. In short, moral norms are truths about how to act in ways that are humanly good (see S.t., 1–2, q. 99, a. 1; S.c.g., 3, 122). It is not the case that any judgment of conscience could as well be reversed if God chose to reverse it. Human nature being what it is, it simply cannot be humanly fulfilling to act contrary to a correct judgment of conscience; and since God is wise and loving, he could not direct us to act against our own well-being (see S.t., 1–2, q. 100, a. 8; S.c.g., 3, 129).
The view that existential principles are established by God’s arbitrary choice is a serious obstacle to evangelization and catechesis. Even those who issue ukases have some end in view—if not the good of their subjects, then their own good. To suggest that God determines right and wrong arbitrarily thus generates the suspicion that God creates us to exploit us. This idea, rejected by Vatican I (see DS 3002/1783), underlies much modern and contemporary rebellion against God, especially the systematic atheism of the various forms of secular humanism (see GS 19–20). The good toward which God directs creation will be treated more fully (19‑A).
13. Perhaps the clearest example of a theory of the sort considered in this question is that of William of Ockham; see Kevin McDonnell, “William of Ockham and Situation Ethics,” American Journal of Jurisprudence, 16 (1971), 25–35. See also Emil Brunner, The Divine Imperative: A Study in Christian Ethics, trans. Olive Wyon (Philadelphia: Westminster Press, 1947), 53, 83, 114–15, and 120.
14. An excellent exegetical study clarifies the nonarbitrariness of God’s commandments: Matthew J. O’Connell, S.J., “The Concept of Commandment in the Old Testament,” Theological Studies, 21 (1960), 351–403.