In Frank Jackson's famous thought experiment, Mary is confined to a black-and-white room and educated through black-and-white books and lectures on a black-and-white television. In this way, she learns everything there is to know about the physical world. If physicalism -- the doctrine that everything is physical -- is true, then Mary seems to know all there is to know. What happens, then, when she emerges from her black-and-white room and sees the color red for the first time? Jackson's knowledge argument says that Mary comes to know a new fact about color, and that, therefore, physicalism is false. The knowledge argument remains one of the most controversial and important arguments in contemporary philosophy.There's Something About Mary -- the first book devoted solely to the argument -- collects the main essays in which Jackson presents (and later rejects) his argument along with key responses by other philosophers. These responses are organized around a series of questions: Does Mary learn anything new? Does she gain only know-how (the ability hypothesis), or merely get acquainted with something she knew previously (the acquaintance hypothesis)? Does she learn a genuinely new fact or an old fact in disguise? And finally, does she really know all the physical facts before her release, or is this a "misdescription"? The arguments presented in this comprehensive collection have important implications for the philosophy of mind and the study of consciousness.