We saw that Anscombe makes the interesting claim that obligation (being bound or required, what one ought to do or needs to do, duty) is inherently diverse, and that some special justification is needed for either treating all 'ought' in action as the same, or holding that there is some uniform 'moral ought' that spans diverse domains of human action. She holds, correctly, that this view was presupposed by some major thinkers in the classical tradition, such as Aristotle (and presumably including also Aquinas); she furthermore maintains that 'modern moral philosophy' unreflectively, and--she thinks--incoherently, presumes, as against the classical tradition, that there is a 'moral ought', while not accepting any framework which could give this presupposition any sense. Among other things, she diagnoses Hume's is/ought quandry as a consequence of the modern viewpoint.
These are interesting claims. They would certainly merit examination in a book on the Nicomachean Ethics, as they would inevitably help to clarify what is distinctive and difficult to grasp in Aristotle's approach.
But Irwin's essay in the recent Kraut collection misfires, because he dramatically misunderstands Anscombe. He takes Anscombe to be claiming that Christian natural law theory is voluntarist; that a commitment to voluntarism sets Aquinas apart from Aristotle; and that the flaw in 'modern moral philosophy' is that it presumes a conception of 'ought' which could have content only by appeal to the will of a divine legislator, the existence of which is denied. The first two claims are false, and Anscombe never held them, and the third claim misconstrues Anscombe's diagnosis. So Irwin's essay ends up being an unneeded lecture, directed against Anscombe, on the theme that Aristotle and Aquinas were not voluntarists.
I give some quotations to show this. Irwin grants the initial plausibility of what he takes to be Anscombe's view as follows:
Evidently, Aquinas believes that there is a divine legislator, and that natural law embodies eternal law, which is not independent of the mind of God. Hence he seems to agree with the Christian view (as Anscombe describes it) against the Aristotelian view, by treating morality as the product of legislation by a divine legislator (p. 326).Note that Irwin is supposing that Anscombe's view, or her view of Christian natural law theory, is that "morality is a product of legislation by a divine legislator."
Irwin then says, correctly, that this is not Aquinas' view, and, taking himself to be arguing against Anscombe, insists repeatedly:
[Aquinas] believes that natural law contains rules, commands, and action-guiding requirements, but he does not argue that law essentially consists in commands that are expressions of the will of a legislator....Irwin follows with a brief summary of non-voluntarist moralists in the early modern and modern periods, saying that these views are at least as plausible as "Anscombe's voluntarism" (p. 330). And he concludes:
Natural law includes commands that do not consist in expressions of the will of any external legislator...
Natural law imposes obligation that does not depend on the will of a legislator...
If we believed Anscombe, we would suppose that Aquinas differs sharply from Aristotle about the moral ought, but we ought not to believe her. If we believed Pufendorf's voluntarism (implicit in Anscombe), naturalists such as Aristotle and Aquinas cannot recognize a moral ought because they cannot recognize external reasons, but we ought not to believe them. (p. 335)All along he seems not to grasp Anscombe's basic challenge--over the uniformity of the notion of 'ought' or requirement.