Zombie-Mary and the Blue Banana On the Compatibility of the 'Knowledge Argument' with the Argument from Modality

This paper is trying to show that it is not possible to use the Knowledge argument as independent evidence for the form of non-reductionism the Modal argument argues for. To show this, Jackson's famous 'Mary' thought experiment is imagined in a zombie world. This leads to the result that there are many problems in the Mary experiment, which cannot have anything to do with phenomenal Qualia, because the Zombie-Mary would encounter them as well, and once all these problems are accounted for, it is no longer clear whether a Zombie-Mary is conceivable at all. Finally, an alternative explanation for the strong non-reductive intuitions of the Mary experiment is discussed. 1. The Epistemic and the Modal Argument Frank Jackson developed one of the most famous thought experiments in the philosophy of mind to prove that physicalism must be false. In this paper I want to argue that this thought experiment confuses two very different ideas about non-reductionism. The first idea is epiphenomenalism, i.e. the idea that there are irreducible phenomenal facts which nevertheless do not influence our behavior, while the second is common sense realism, which I take to be the idea that an irreducible phenomenal consciousness (i.e. a consciousness that includes phenomenal facts which are neither type nor token identical with physical facts) is causally relevant for at least parts of our behavior. This second alternative must, of necessity, doubt in some way one of the central claims of physicalism, i.e. that there is in our world a physical cause for every physical effect. If this suspicion is correct, then the thought experiment featuring the omniscient but blindblind scientist Mary invokes intuitions which have nothing to do with the first idea of non-reductionism. Understanding the experiment in this way changes it into what Daniel Dennett has labeled an intuition pump. It would be rendered no more than one of these "fiendishly clever devices" which "deserve their fame, if only for their seductiveness" (Dennett 1991, p.282). This is to say that Mary prompts intuitions of common sense realism which obviously cannot be reconciled with the theoretical position of epiphenomenalism. And this in the light of the fact that the Mary experiment is used by many, including its inventor, to support precisely this latter position. But first of all, let us examine Jackson's argument. Imagine this intuitively very convincing thought experiment: "Mary is confined to a black-and-white room, is educated through blackand-white books and through lectures relayed on black-and white television. In this way she learns everything there is to know about the physical nature of the world. She knows all the physical facts about us and our environment, in a wide sense of 'physical' which includes everything in completed physics, chemistry, and neurophysiology, and all there is to know about the causal and relational facts consequent upon all this, including of course functional roles. If physicalism is true, she knows all there is to know. For to suppose otherwise is to suppose that there is more to know than every physical fact, and that is what physicalism denies. Physicalism is not the noncontroversial thesis that the actual world is largely physical, but the challenging thesis that it is entirely physical. This is why physicalists must hold that complete physical knowledge is complete knowledge simpliciter. For suppose it is not complete: then our world must differ from a world, W(P), for which it is complete, and the difference must be in non-physical facts: for our world and W(P) agree in all matters physical. Hence, physicalism would be false at our world (though contingently so, for it would be true at W(P)). It seems, however, that Mary does not know all there is to know. For when she is let out of the black-and-white room or given a color television, she will learn what it is like to see something red, say. This is rightly described as learning-she will not say, "ho,hum". Hence physicalism is false." (Jackson 1986, p.291). It is almost impossible not to feel the intuitive force of this experiment. Intuitively, all the physical knowledge in the world cannot give Mary the slightest clue about the experiential feel of seeing colors. Jackson concluded from his experiment that this feel can therefore play no role in the functional description of our world, i.e. that this feel must be epiphenomenal. The thought experiment evoked a host of other philosophical interpretations as well, many agreeing, but even more criticizing, the conclusion of Jackson's argument. These critical voices were very heterogeneous in themselves. They ranged from a complete denial of the conclusion of the experiment (Dennett, 1991), through the claim that Mary gained a new ability but no knowledge (Nemirow, 1990), to various forms of replies that found in the Mary experiment evidence for the intricacies of the term knowledge, knowing how and knowing that, indexical arguments, opacity of knowledge, e.g. (Horgan, 1984; Perry, 1979). There is much to be learned from this debate, but this paper focuses exclusively on the question of whether the experiment can provide independent evidence for the ontology advocated by the epiphenomenalist <1>, as it was intended to by Jackson and as many philosophers have thought after him. This essay is trying to provide a tool that allows philosophers and non-philosophers alike not to get misled by the thought experiment as easily as in the past. It wishes to argue that the Mary experiment does not provide support for the theoretical position it was originally designed to defend and which David Chalmers <2> has made such a very strong and famous case for, i.e. epiphenomenalism. The Mary experiment might be compatible with this position, but cannot provide any evidence for it. These points can be made by demonstrating that the intuitions Mary evokes relate problematically to another classical piece of ammunition within the epiphenomenalist artillery. In fact, Jackson's description of the purely physical world W(P) is strongly reminiscent of another very interesting philosophical creature. Probably the only other being that has become as famous as the conclusive proof against reductionism is the zombie <3>. A philosophical zombie is, as no philosopher ever forgets to mention, quite different from a voodoo zombie. Where the latter is essentially something with a frighteningly different appearance and terrifying behavior in comparison to a normal human being, the philosophical zombie is exactly like a human being, with one small but decisive exception. It does not have phenomenal consciousness. In some versions, philosophical zombies are only behaviorally indistinguishable from their conscious fellow beings whereas in other, more extreme cases, zombies are supposed to be exact physical replicas of their conscious twins, which therefore must be behaviorally isomorphic to their conscious counterparts as well. Many people find these creatures difficult to imagine, so it might be useful to emphasize once more: What sets them apart from human beings is nothing else but a complete lack of phenomenal consciousness. Zombies do not have Qualia. Qualia are conscious qualities <4> this means that they are the experiential properties of our feelings, thoughts, impressions, etc. They are 'what it is like' to have all these things. The zombie argument is supposed to show that, as it is conceivable to imagine a world that is just like ours apart from the nonexistence of Qualia, it cannot be possible that Qualia can be reduced to something else (typically a purely functional description) in ours. This is not to say that zombies do not talk about Qualia! As they are behaviorally equivalent to us, they can be imagined to talk about consciousness just as much as we do. Only in their case, the only reason for their doing so is the complex architecture in their brain. But all the neural firing that is going on in their heads does not give them the phenomenal side of consciousness.