 Before we consider the compatibilist’s replies, one clarification of the reductio is in order. For it may be unclear whether EXT entails (1) in the first place (whether apriori or not). However, if EXT is derived from one of the causal theories of content (from section  1),  then acquiring the water concept requires causally interacting with water (if only via your linguistic community). (See McGinn 1989, ch. 1 passim, McCullough 1999, but contrast with McLaughlin &amp; Tye 1998a, Ball 2007.) Thus possessing the concept requires the existence of water, meaning that the view entails (1). Even so, if the incompatibilist wants to add that (1) is entailed apriori, she would need the contentious premise that some causal theory of content is entirely apriori.