 The claim that the concept of belief is primary to that of desire can be questioned. Thus, there is empirical evidence from developmental psychology that children acquire the concept of desire prior to acquiring that of belief (Wellman 1993). It has also been argued that belief and desire are conceptually interdependent (Miller 2008). More importantly, even if it can be shown that the concept of belief is primary to that of desire, and of the other propositional attitudes, the question arises whether indeed one could not grasp the concept of content without grasping that of belief. Prima facie, grasping the concept of a propositional attitude such as belief is rather distinct from grasping the concept of content, since it involves the idea of taking up an attitude towards  content.[52]  Moreover, Boghossian is committed to the strong claim that opponents of content normativity fail to grasp the concept of content (or, alternatively, that they operate with a different concept).