The non-consequentialist moral force of promises: a response to Sinnott-Armstrong
That we have a duty not to break a promise is often presented as a reason to reject consequentialism. Sinnott-Armstrong has argued, however, that in fact consequentialism provides the best account of the duty not to break a promise (2009; see also Sinnott-Armstrong 1992). I will argue that Sinnott-Armstrong’s argument fails. The phenomena of promising remain a reason to reject the view that all of morality consists in our duty to produce the best consequences. That is not to say that we do not have a duty to produce the best consequences. Rather, the duty to produce the best consequences is, like the duty not to break a promise, one of a plurality of moral duties. According to Sinnott-Armstrong, the best explanation of the strength of one’s duty to keep a promise is that the duty’s strength is based on the consequences of breaking the promise. This is because if the consequences of keeping a promise vary, then the strength of one’s duty to keep the promise will vary as well; while if the consequences of keeping a promise do not vary, the strength of the duty will not vary even if all the other circumstances surrounding the promise do vary. And, applying Mill’s method of concomitant variation, Sinnott-Armstrong maintains that ‘since the strength of a moral obligation goes up and down as the harms in violating it go up and down, this correlation supports the hypothesis that the harms of violating it are what makes the moral obligation as strong as it is’ (2009: 440). Moreover, Sinnott-Armstrong argues, if the strength of the duty to keep a promise is based on the consequences of breaking it, then the best explanation of the existence of the duty must be consequentialist as well. The only way to rebut this consequentialist argument is ‘to explain why some moral obligations are stronger than others without invoking the harmful