According to objectivism about the practical 'ought', what one ought to do depends on all the facts; according to perspectivism, it depends only on epistemically available facts. This essay presents a new argument against objectivism. The first premise says that it is at least sometimes possible for a normative theory to correctly guide action. The second premise says that, if objectivism is true, this is never possible. From this it follows that objectivism is false. Perspectivism, however, turns out to be compatible with the plausible assumption about guidance.
I defend the two premises on the basis of an account of what it is for a normative theory to guide action. Central to this account is the idea that correct action-guidance involves correct practical reasoning from a normative theory to an action, which requires (among other things) that agents have the capacity to believe for the right reasons. Since objectivists about the practical 'ought' are committed to objectivism about the epistemic 'ought', it follows that agents lack this capacity and so are in principle unable to be correctly guided by a normative theory. This shows that recent attempts to reconcile objectivism with action-guidance are unsuccessful, which all assume that, if objectivism is true, it is at least sometimes possible for a normative theory to correctly guide action.
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