 Constructivism’s insight is that practical truths should be explained in terms of the constitutive features of practical reasoning, which the notion of ‘construction’ is supposed to capture. But critics argue that the constructivist conception of practical reasoning is either arbitrary or parasitic on independent moral values. The objection often takes the form of a metaethical dilemma similar to the dilemma discussed by Plato in the Euthyphro (10a). Either the practical standpoint is subject to moral constraints or it is not. If it is not, then 