A challenge for Humean externalism

Humean externalism is the view that moral motivation must be explained in terms of desires that are “external” to an agent’s motivationally-inert moral judgments. A standard argument in favor of Humean externalism appeals to the possibility of amoral or morally cynical agents—agents for whom moral considerations gain no motivational traction. The possibility of such agents seems to provide evidence for both the claim that moral judgments are themselves motivationally inert, and the claim that moral motivation has its source in desires external to those judgments. This essay makes the case that, rather than providing a compelling argument in favor of Humean externalism, the argument from amoralism can be recast to set up an important challenge to this view. On one hand, it appears that the central methodological considerations and types of evidence that undergird the externalist argument from amoralism are in tension with a central Humean commitment: namely, that desires can be sources of motivation. While it is possible for Humeans to escape this horn of the dilemma, the most plausible strategies for doing so can be co-opted by internalists to resist the argument’s externalist conclusion.