 Several philosophers appeal to the understanding in their accounts of a priori justification: Bealer in all his many essays; BonJour 1998; Jackson 2000; Peacocke 2000; Sosa 2013: 199; Boghossian: forthcomingb. But the view also has its critics. Though Paul Boghossian thinks that some a priori justification stems from that source, he thinks that a priori intuitions about substantive normative propositions can provide justification but they do not rest on our understanding those propositions (forthcomingb). Consider the proposition that It is always wrong to torture children just for the fun of it. His argument is that if such intuitions were based on understanding the concept “wrong”, then it would not make sense to ask whether that sort of act merits disapproval or should be punished, assuming for the sake of argument that the correct account of the non-substantive meaning of “wrong” is in terms of what merits disapproval or should be punished. But he thinks that this question always makes sense. So it follows that a priori normative intuitions of this sort are not based on understanding the relevant normative concepts. Boghossian seems to think that this argument generalizes to apply to all a priori intuitions whose objects are synthetic propositions, not just to intuitions about substantive normative propositions.