 The issue is that EXT seemingly implies that knowing about content requires knowing about the environment. And since the latter is empirical, so too would be the former, contra  SK.[4]  Now it is usually thought that, if EXT is incompatible with SK, this would be a serious problem for EXT (though some think internalism also conflicts with SK; see McLaughlin &amp; Tye 1998a, Farkas 2003, Bar-On 2006, p. 434). Yet some think the incompatibility threatens SK instead of EXT (see section  2.4).  Regardless, the interest in the debate goes beyond EXT, for it pertains to many central concerns of philosophers, such as the nature of knowledge and the relation between mind and world. The debate also touches on more specialized topics, including memory, concept acquisition, epistemic responsibility, and transcendental arguments.