Abstract

Must an acceptable moral theory be systematic and complete? Most philosophers agree we have no such theory now---at least not one which is plausible in other respects. But perhaps we should strive for such a theory and regard our current incomplete theories as at best useful stepping stones. Some theories, such as hedonistic utilitarianism, hold out the promise of being complete: provided all the empirical facts one could, in principle, determine whether any given act was right or not. Other theoretical approaches seem much further from being complete, and it is not obvious how they might be refined to become fully complete in the future. Though completeness is surely not the only reason for thinking a theory acceptable, is it some reason? ;I approach this question by considering, at first, Henry Sidgwick's views. Sidgwick's defense of utilitarianism is often dismissed on the grounds that it relies on a spurious moral epistemology: rational intuitionism. This worry is based on a misunderstanding, though. Once we properly appreciate the way Sidgwick employs the notion of an "intuition," we can see that Sidgwick does not rely on those features of rational intuitionism that most philosophers find objectionable. By contrast, I claim that Sidgwick does rely on a powerful and under-examined assumption about the standards a fully acceptable moral theory must meet. Specifically, I show that Sidgwick relies upon the claim that any ideally acceptable moral theory must enable us, in principle, to determine the rightness of any act, provided all the empirical facts. I call this the Completeness Assumption. ;Some may find Sidgwick' reliance on such an assumption every bit as suspicious as any reliance on rational intuitionism. Against this, I argue that plausible views about the nature of morality provide the resources for a powerful argument in favor of the Completeness Assumption. ;Many philosophers have objected to the Completeness Assumption. I argue that contemporary attempts to reject the Completeness Assumption misfire. Thus, I claim we have good reason to accept the Completeness Assumption. ;However, the fact that a theory satisfies the Completeness Assumption turns out not to be a reason to accept it. Consequently, Sidgwick's argument in favor of utilitarianism is a failure. Those who advance theories and methods that are less systematic and complete need not fear the Completeness Assumption. Those who have tried to resist the Completeness Assumption have done so needlessly