 Nevertheless, it can be debated whether EXT entails the “shifty” theory of memory. When Burge first presented his Twin Earth experiment, he conceded that it does not show that all mental contents satisfy EXT (though it suggests that that is typically so) (1979, p. 92, passim). The contents of memory thus might be an exception. And indeed, Burge (1993; 1998) endorses the view that memory should “preserve” past thought contents. So in a slow switch case, Burge holds that Oscar’s properly functioning memory preserves an Earthian thought content, so that the very same content is available later for recall.