 It is the second sense of “what it’s like” that figures in anti-materialist arguments from subjects’ “knowing what it’s like,” primarily Nagel’s (1974) “Bat” argument and Jackson’s (1982) “Knowledge” argument, Chalmers’ (1996, 2003) Conceivability argument, and Levine’s (1983, 2001) Explanatory Gap arguments. To begin with the first of those: Jackson’s character Mary, a brilliant color scientist trapped in an entirely black-and-white laboratory, nonetheless becomes omniscient as regards the physics and chemistry of color, the neurophysiology of color vision, and every other public, objective fact conceivably relevant to human color experience. Yet when she is finally released from her captivity and ventures into the outside world, she sees colors for the first time, and learns something: namely, she learns what it is like to see red and the other colors. Thus she seems to have learned a new fact, one that by hypothesis is not a public, objective fact. It is an intrinsically perspectival fact. This is what threatens materialism, since according to that doctrine, every fact about every human mind is ultimately a public, objective fact.