What Didn’t Mary Know?

Jackson’s account of qualia is troubled by neither of these problems. His thought experiment2 does not presuppose the existence of non-physical qualia but, rather, attempts to pick them out of something he believes to be a feasible state of affairs. Jackson introduces us to Mary, a gifted scientist specializing in colour. Mary conducts all of her research from a black and white room with a monochrome television – indeed she has never seen colour – and, because she is so brilliant, proceeds to learn “all the physical information” about colour (Jackson 342). Having discovered every physical fact there is to know related to her field, Mary decides to take a stroll outside her room, so she steps outside and sees colour for the first time. Jackson argues that when Mary does this, it “seems just obvious that she will learn something about the world and our visual experience of it” (342). Clearly, Jackson reasons, Mary’s previous knowledge was incomplete, even though it included every physical fact. Jackson tells us specifically that “qualia are left out of the physicalist story” and, consequently, physicalism is false (342).

Recall that as an epiphenomenalist Jackson holds that these qualia are not only non-physical but, crucially, non-causal: their “possession or absence makes no difference to the physical world” (344). Though Jackson holds that Mary “will learn something” when she sees colour, his epiphenomenalist definition of qualia commits him to the belief that qualia could not be the cause of this learning. If qualia were the cause, then Mary’s learning could not have any effects on the physical world; learning could not even be a physical aspect of the mental. Indeed, Campbell recognizes essentially this point when he admits that “the experience of the quality in question [qualia] is inoperative in behaviour, even the behaviour in which such experiences [qualia] are described” (337). In short, if non-physical qualia were the cause of what Mary learned, then she could never show it, nor could she even know that she had learned it. This does not seem to be the sense in which we intuitively attribute learning to Mary.

Given that it seems intuitive that a proper understanding of learning should involve its ability to lead to behaviour, then Mary’s learning was not caused by qualia. Instead, it must have been caused by something physical, for it could not have simply popped into existence. However, if this is the case, then Jackson did not tell us the whole story when he argued that qualia were left out of the physicalist story (342): indeed, something physical was left out as well! It appears strangely paradoxical that the physicalist story could leave out something physical, but this is what Jackson’s epiphenomenalist views seem to entail. To avoid this contradiction, we could reject Jackson’s premise that Mary knew every piece of information before she stepped into the world of colour, if we are to accept what he sees as “just obvious”, that she learned something new (342). Interestingly, Nagel’s account of qualia allows for exactly this possibility. Just as, Nagel admits, there might be physical facts about what it is like to be a bat “beyond the reach of human concepts” (325), so too there might be facts about colour that Mary could not have grasped through a purely objective analysis. If, as Nagel suggests, the physical world is not fully describable in objective terms, then Mary could never have been as brilliantly knowledgeable as Jackson supposes. By Nagel’s account, we cannot accept Jackson’s premise that Mary knew “all the physical information” (342). In attempting to escape Campbell’s method of presupposition, Jackson falls prey to a troublesome premise of his own.

The intuition upon which Campbell and Jackson base their epiphenomenalist claim that qualia must be non-physical forces them to argue that qualia are also non-causal, leading to serious problems: the Imitation Man thought experiment, in order to be conceptually possible, requires Campbell to presuppose what it is designed to prove, while Jackson stipulates that Mary must know what she cannot. In addition, the epiphenomenalist intuition requires that we accept highly counterintuitive definitions of words like “torture” and “learning”. These arguments cast considerable doubt on Campbell’s and Jackson’s mutual conclusion that physicalism is false. Nagel’s analysis, in contrast, is less problematic. It allows qualia to be physical and causal while suffering none of the weaknesses that plague Campbell’s and Jackson’s arguments. Nagel cannot presume, nor can we, that physicalism is mistaken.