The core chapters of Gill's book began as articles, which he has here assembled with new material into an engaging defence of moral pluralism. Not to be confused with relativism, he defines pluralism as the view that there are multiple ultimate moral ends, and that there is no available principle or ordering system which will, in all possible cases, resolve those ends into a single, right course of action. This view stands most obviously in opposition to moral monism, such as Mill's (the one ultimate end is happiness) and Kant's. It also opposes, less obviously, what Gill calls multiplism: the view that, although there are multiple ends, there are always principles available to guide their application. For example, obeying God and loving neighbour might both be ultimate ends, but in cases of conflict, if we say that one takes priority over the other, then we are a multiplist. Gill argues that pluralism is superior to both alternatives. In an impressive final chapter, he shows how the pluralist can accommodate ‘agonizing decisions’ better than either the multiplist or the consequentialist (who shrugs, ‘Of course you ought to kill the friendless tramp to harvest his organs; what's so agonizing about that?’).
As his title indicates, Gill defends one particular version of pluralism: Hume's. This self-conscious use of the history of ideas is one of the book's strengths. Despite engaging analytic philosophers like W. D. Ross, Gill avoids the common pitfall of neglecting that our concepts come from somewhere. How we conceive an idea today depends on how the idea reached us and, as Gill shows, pluralism reached us via a series of challenges to natural law. Various Christian theologians struggled to meet these challenges. When they dropped the ball, Hume picked it up and ran with it.
Though this part of Gill's argument is very brief, it will be worth a bit more attention for theologians. Gill shows that Christian ethics in early modern Britain was multiplist, with preachers and scholars almost universally endorsing a tripartite structure: worship God, love self, love neighbour. It was the philosopher and Church of Scotland minister, Frances Hutcheson, however, who sent us down a different path. In an (understandable) effort to thwart Hobbes’ egoism, Hutcheson fatefully embraced monism: benevolence (not selfishness, as Hobbes had said) was the single, ultimate end. This set a trajectory which resulted in the unfortunate triumph of monism, though in two flavours: Mill's and Kant's.
Gill wants to retrace our footsteps back up the path to Hume, so that we can take the missed fork in the road: the path to pluralism. Part of the book's value is in showing how certain trends in moral philosophy today harken back to that missed fork, reinforcing Gill's suspicious that we should have followed it in the first place. This includes recent recoveries of sentimentalism (like Haidt's), certain trends in moral psychology and so on.
That pluralist path might be inviting for those who share Hume's religious scepticism; could Christians follow? That depends. What is at stake theologically in the choice between monism, multiplism and pluralism? Gill grants as a hypothetical that God may be a monist even if humans ought not to be. That seems plausible (even the Westminster Catechism has two ends for humans, not one). The deeper issue is whether Gill blurs the lines between pluralism and multiplism. As far as I can tell, by Gill's definition I am myself a pluralist, but I also think I am (broadly) Thomist, which should make me a multiplist.
I think the real choice actually lies between those committed to ordering all goods via an analytic procedure, as in maths, and those who weigh them aesthetically, as with artistic beauty. (Hume calls these alternatives ‘geometrical truth’ and ‘criticism’.) This choice cuts across the multiplist–pluralist divide. Gill hints in this direction, but never follows through. To my notice, he never even cites ‘Of the Standard of Taste’, an essay where Hume himself appears more multiplist. I think Christians have good reason to pursue that side to Hume; indeed I think that was actually Hutcheson's view. Contra Gill, I don't read Hutcheson as rejecting pluralism so much as finding monism a convenient rebuttal to Hobbes.
I mentioned above Gill's final chapter on agonising decisions. He here uses Grace Kelly's High Noon character, Amy Kane, to great effect. In the film, Kane (rightly?) shoots a villain despite her pacifism, and (rightly?) experiences remorse. Gill takes this to be a vote in pluralism's favour: non-pluralists hold that, if the shooting was right, the remorse is misplaced, or if the remorse is justified then the shooting was not. Gill's analysis of the film is terrific, though I think it poses a theological puzzle he cannot answer. The traditional Christian answer to the puzzle is sin, a sufficiently rich account of which captures Amy Kane much better than Hume's moral psychology (recall that in the film, Kane is a Christian). Yet this poses a challenge to Christians too, at least of the Thomist sort, for whom it is difficult to fit sin together with moral tragedy. I take this to be a vote in pluralism's favour as well.
