Understanding the Ethics of Changing Moral Dispositions

People have moral dispositions, parts of their moral psychologies that determine how they act in moral contexts. These dispositions are subject to influence and change, ever more so as we discover more about them and what we can do to effect change in them. This forces us to consider which things ought to impact these dispositions, which things are legitimate influences upon them. I argue that - other considerations aside - perceived relevant reasons ought to influence these moral dispositions. Ceteris paribus, it's always better that such reasons influence moral dispositions, yet better when more do, worse when none do yet dispositions still change. I show this to be the case by analysis of thought experiments which hold other variables constant and propose that this is the case because we demand that behaviour properly connects with and responds to the reasons agents have. I argue that this understanding, captured in what I call a 'rationalizability requirement' on moral-dispositional change, has important implications. It refutes what I call 'instrumentalism' about moral-dispositional influencing; the view that the only thing that matters in evaluating such influencing is results (broadly construed). Methods, it turns out, matter. It also helps us to evaluate techniques used in advertising, brainwashing, moral bioenhancement and nudging. It does all these things, I contend, while garnering additional support from those who value freedom, construed as autonomy or as interpersonal non-domination, and thereby unifying (at least in practice) influential extant perspectives on the evaluation of moral-dispositional influencings into a single standard.