Online research in philosophy

Philosopher's zombies are hypothetical beings behaviorally, functionally, and perhaps even physically indistinguishable from normal humans, but who lack our consciousness. Many people seem to be convinced that such zombies are a real conceptual possibility, and that this bare possibility entails that understanding human consciousness must remain forever beyond the reach of science. However, the conceptual entailments of zombiehood have not been sufficiently examined. This brief article shows that any way of understanding the behavior of zombies that does in fact support the suggested entailment, leads to contradictions and absurdities. Zombies are _not_ conceptually possible.

I argue that zombies are inconceivable. More precisely, I argue that the conceivability-intuition that is used to demonstrate their possibility has been misconstrued. Thought experiments alleged to feature zombies founder on the fact that, on the one hand, they _must_ involve first-person imagining, and yet, on the other hand, _cannot_. Philosophers who take themselves to have imagined zombies have unwittingly conflated imagining a creature who lacks consciousness with imagining a creature without also imagining the consciousness it may or may not possess.

According to the zombie conceivability argument, phenomenal zombies are conceivable, and hence possible, and hence physicalism is false. Critics of the conceivability argument have responded by denying either that zombies are conceivable or that they are possible. Much of the controversy hinges on how to establish and understand what is conceivable, what is possible, and the link between the two—matters that are at least as obscure and controversial as whether consciousness is physical. Because of this, the debate over physicalism is unlikely to be resolved by thinking about zombies—or at least, zombies as discussed by philosophers to date.



In this paper, I explore an alternative strategy against the zombie conceivability argument. I accept the possibility of zombies and ask whether that possibility is accessible (in the sense of ‘accessible’ used in possible world semantics) to our world. It turns out that the question of whether zombie worlds are accessible to our world is equivalent to the question of whether physicalism is true. By assuming that zombie worlds are accessible to our world, supporters of the zombie conceivability argument beg the question against physicalists. I will then consider what happens if a supporter of the zombie conceivability argument should insist that zombie worlds are accessible to our world. I will argue that the same ingredients used in the zombie conceivability argument—whatever they might be—can be used to construct an argument to the opposite conclusion. If that is correct, we reach a stalemate between physicalism and property dualism: while the possibility of some zombies entails property dualism, the possibility of other creatures entails physicalism. Since these two possibilities are inconsistent, one of them is not genuine. To resolve this stalemate, we need more than thought experiments.

A philosophical zombie is a being indistinguishable from an ordinary human in every observable respect, but lacking subjective consciousness. Zombiehood implies *linguistic indiscriminability*, the zombie tendency to talk and even do philosophy of mind in language indiscriminable from ordinary discourse. Zombies thus speak *Zombish*, indistinguishable from English but radically distinct in reference for mental terms. The fate of zombies ultimately depends on whether Zombish can be consistently interpreted. If it can be interpreted consistently, then zombies remain possible, but no test could ever reveal whether anyone (oneself included) is speaking Zombish. Any materialist theory of consciousness is therefore already a theory in Zombish, and is equally confirmable in its human language edition (applicable to humans) and its zombie-language edition (applicable to zombies). On the other hand, if Zombish cannot be consistently interpreted, then the zombies described in Zombish are logically impossible. Either way, the search for a materialistic theory of consciousness should be untroubled by the (possible) zombies among us.

A prevailing view in contemporary philosophy of mind is that zombies are logically possible. I argue, via a thought experiment, that if this prevailing view is correct, then I could be transformed into a zombie. If I could be transformed into a zombie, then surprisingly, I am not certain that I am conscious. Regrettably, this is not just an idiosyncratic fact about my psychology; I think you are in the same position. This means that we must revise or replace some important positions in the philosophy of mind. We could embrace radical skepticism about our own consciousness, or maintain the complete and total infallibility of our beliefs about our own phenomenal experiences. I argue that we should actually reject the logical possibility of zombies.

A zombie is a creature just like a conscious being in certain respects, but wholly lacking in consciousness. In this paper, I look at zombies from the perspective of basic ontology (“from below”), taking as my starting point a trope ontology I have defended elsewhere. The consequences of this ontology for zombies are mixed. Viewed from below, one sort of zombie—the exact dispositional zombie—is impossible. A similar argument can be wielded against another sort—the exact physical zombie—but here supplementary principles are needed to get to the impossibility result. Finally, at least two sorts of zombie—the behavioural and functional zombies—escape these arguments from below.

From the AI point of view, consciousness must be regarded as a collection of interacting processes rather than the unitary object of much philosophical speculation. We ask what kinds of propositions and other entities need to be designed for consciousness to be useful to an animal or a machine. We thereby assert that human consciousness is useful to human functioning and not just and epiphenomenon. Zombies in the sense of Todd Moody's article are merely the victims of Moody's prejudices. To behave like humans, zombies will need what Moody might call pseudo-consciousness, but useful pseudo-consciousness will share all the observable qualities of human consciousness including what the zombie will be able to report. Robots will require a pseudo-consciousness with many of the intellectual qualities of human consciousness but will function successfully with few if any human emotional conscious qualities if that is how we choose to build them.

Todd Moody’s Zombie Earth thought experiment is an attempt to show that ‘conscious inessentialism’ is false or in need of qualification. We defend conscious inessentialism against his criticisms, and argue that zombie thought experiments highlight the need to explain why consciousness evolved and what function(s) it serves. This is the hardest problem in consciousness studies.