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Hollywood producers are not the only ones who think that zombies exist. Some philosophers think that too. But there is a tiny difference. The philosophers' zombie is not an inelegantly walking corpse that stinks (like in the movie "Dawn of the Dead") and makes strange sounds, but a creature that is very similar to a normal human being. In fact, there is only one thing that makes a difference between an ordinary human being and a zombie - zombie is not a conscious being. In other words, zombie is an imaginary being that looks like a human being, talks like a human being, smells like a human being, passes the Turing test like an ordinary human being... but it doesn't have a conscious experience like a human being does. Zombie is lacking a subjective feeling of what it is like to be a zombie - there is nobody at home. Can you imagine that your wife or girlfriend is a zombie? Hmm, maybe that is not so hard to imagine. But can you imagine that your friends are zombies? Or, if we want to be radical, that all human beings are zombies? Including you? Are those philosophers who think that a conscious experience is what makes a difference between human beings and zombies - zombies as well? Well, why not? Dennett thinks that it is acceptable to say: "We're all zombies". (Dennett 1991: 406). How is it possible for a serious philosopher to claim something like that?

The zombie problem is a philosophical problem and hints to it can be found even in the Putnam's critique of the behavioral theory of mind. In his argument about the possibility of a Superspartan, an imaginary being that doesn't behave as if it were in pain, but feels an intense pain, Putnam revealed the flaws in the behavioral theory of mind (Putnam 1961: 29-34). Something quite different would be a Superactor, an imaginary being that successfully acts as if it felt an enormous pain, but feels no pain at all. That Superactor is a hint of a zombie, a hint of a being that is, in an extreme case, just "... something physically identical to me, but which has no conscious experience - all is dark inside". (Chalmers 1996: 96). Even those arguments of Putnam's suggest that there is something that is not visible from the outside, from the third-person approach. That "invisible thing", or "special ingredient" as Dennett calls it, is the main point of a zombie thought experiment. Consciousness, as we commonly think of it, is something interior and private. Some philosophers find it very plausible to think that it is possible to conceive a "human being" that lacks those interior and private conscious experiences. Such a being they name zombie. We can know many things about zombies: their way of doing things, their functioning in everyday situations, even their chemical structure... but we cannot know whether there is anybody at home. So, they think, zombies are in all respects like human beings, with one slightly difference: they are unconscious.

Philosophical considerations about the possibility of zombies make Dennett feel ashamed of being a philosopher. He says: "...it is an embarrassment to our discipline that what is widely regarded among philosophers as a major theoretical controversy should come down to whether or not zombies (philosopher's zombies) are possible/conceivable" (Dennett 1995: 177). In his Consciousness Explained Dennett writes: "(It's hard for me to keep a straight face through all this, but since some very serious philosophers take the zombie problem seriously, I feel obliged to reciprocate.)" (Dennett 1991: 95). Hence, for Dennett, an intuition about the possibility of zombies is not a good starting point of the philosophy of consciousness. Why not? Because if there is a possibility of zombies, than it is impossible to approach consciousness from the third-person's point of view. And in that case, consciousness remains a mystery, something that cannot be an object of science, because all science is made from the third-person's point of view. It is unacceptable for Dennett to admit that consciousness is a mystery beyond science. And philosophy that admits that consciousness is a mystery is an obstacle to the science of consciousness. If zombies are possible, than there is no public criterion that can help us in making a difference between a zombie and a conscious human being. And epiphenomenalism and dualism are not scientifically fruitful.

However, there are still many philosophers that seriously consider the problem of zombies. Dennett calls them Zombists (John Searle, David Chalmers, Joseph Levine, Colin McGinn, and Thomas Nagel are mentioned). The zombists are "...united in the conviction that there is a real difference between a conscious person and a perfect zombie - let's call that intuition the Zombic Hunch - leading them to the thesis of Zombism: that the fundamental flaw in any mechanistic theory of consciousness is that it cannot account for this important difference" (Dennett 2005:14). That hunch suggests that consciousness or conscious experience is something in addition to or something beside the process that happens in brain. That kind of thing cannot be fully explained by explaining the mechanisms of consciousness. In order to show that the Zombic hunch is not a good way of thinking about consciousness, Dennett must find other intuitions, which offer a better way of thinking about consciousness.

The question is: How can we dispel the magic of the Zombic hunch? How can we escape such a strong intuition? Is there a stronger intuition? Dennett admits that he is also visited by the Zombic hunch, but he doesn't credit it as the Zombists do (Dennett 2005: 14). On the other hand, he credits an intuition that I will call the Zimboic Hunch.

The Zombie thought experiment is all about a possible or conceivable situation. For Dennett, thought experiments in general are nothing but intuition pumps, since they cannot be used as a method of verification of the validity of our hypothesis (as it is possible in scientific experiments). "They are more art than science." (Dennett 1991: 440). The main defectiveness of thought experiments is that "...people don't actually imagine the case in the detail that it requires" (Dennett 1991: 436). But details do matter. Complexity does matter. "The most influential thought experiments in recent philosophy of mind have all involved inviting the audience to imagine some specially contrived or stipulated state of affairs, and then - without properly checking to see if this feat of imagination has actually been accomplished - inviting the audience to "notice" various consequences in the fantasy" (Dennett 1991: 282). Details are important and "the force of such an argument depends critically on how high one's standards of conception are" (Dennett 1991: 282). When a Zombist claims that he can conceive a zombie, we have to ask him: Oh, really? "Can you really imagine a zombie?" (Dennett 1991: 282). Can you really imagine a being that is indistinguishable from a normal human being, but lacks conscious experience? I can't.

In order to break the zombie spell, Dennett introduces the concept of zimbo. Everyone who thinks that a zombie is possible must also admit that a zimbo is possible. "A zimbo is a zombie that, as a result of self-monitoring, has internal (but unconscious) higher-order informational states that are about its other, lower-order informational states... A zimbo is just a zombie that is behaviorally complex; thanks to a control system that permits recursive self-representation". (Dennett 1991:310). Zimbo can successfully pass the Turing test. Zimbo has an inner life. Zimbo has a unique point of view. However, zimbo is just a complex zombie that, owing to its complexity, has beliefs about beliefs and beliefs about its other states. "What zimboes have that zombies do not is a sophisticated internal mechanism - they are functionally complex". (Polger 2000: 268). Zimbo is just a zombie that believes that it is conscious or that it has conscious states.

Dennett thinks that the human being is a zimbo that: "...would (unconsciously) believe that it was in various mental states... It would be the 'victim' of the benign user illusion of its own virtual machine!" (Dennett 1991: 311). If human beings are zimboes, that is a special kind of zombies, then Dennett's pronouncement that "We're all zombies" can be seen in a different light. What Dennett wants to say is that, in spite of the fact that we are not conscious (at least not in a way we have thought we are), we truly believe that we are.

Dennett has a Zimboic Hunch: the hunch that human beings only believe that they are conscious. It is not that human beings don't have the belief that they are conscious but rather that the belief is all there is. The conscious experiences themselves are missing. There is no consciousness besides the belief that there is consciousness. The consciousness itself is missing. Why does Dennett think that this is a good way to build the theory of consciousness?

Let's see the other side. Zombists speak about the four levels of data that the theory of consciousness must take into consideration:

For the Zombists, the primary data to which a theory of consciousnesses must answer are the "conscious experiences themselves". Dennett disagrees. He thinks that it is enough to stop at (b), namely the beliefs about these conscious experiences, i.e. he claims that such beliefs are the primary data of an adequate theory of consciousness. His explanation of this conclusion is: "If you have conscious experiences you don't believe you have - those extra conscious experiences are just as inaccessible to you as to the external observers. So a first person approach garners you no more usable data than heterophenomenology does... if you believe you have conscious experiences that you don't in fact have - then it is your beliefs that we need to explain, not the nonexistent experiences". (Dennett 2005: 45). In other words, if we explain the beliefs about the conscious experiences, we have explained everything that could be explained.

However, we don't have to explain something that doesn't exist (conscious experiences themselves). If we explain those false beliefs about consciousness, we have done the job. Conscious experiences don't exist beside those beliefs about them. "The Copernicans thought that they did not have to explain the sun's motion, because it was enough to explain why the sun was believed to move". (Rorty 1993: 184) The same is valid for the beliefs that we have conscious experiences. We are the victims of a false belief that we are conscious. Just like the zimboes. Therefore, it is plausible to say that we are all zimboes, a kind of complex zombies.

Why does Dennett find it plausible? This way of thinking about consciousness excludes the possibility of thinking about consciousness as some "special ingredient" (zombies don't have it!) that can be found in addition to the existing functional role of the human brain. In other words, if a being is functionally identical to the conscious being, then that being is also conscious. That is the Dennett's way of demystifying consciousness. And if consciousness is something like what Dennett thinks it is, than it can be an object of scientific investigation.

If you want to believe that all human beings are zombies, you have to agree with Dennett on the following:

What is then left of our zombic hunch? Is it still as convincing and obvious as it was before? Or has Dennett really managed to dispel its magic? Is the zimboic hunch a more plausible intuition than the zombic hunch? For the rest of us, the question that remains is the following: What is it like to be a zimbo? Well, we can tell stories about our inner world, even stories about our consciousness. But beside these stories - is there anything left?

Block, Ned (1980) (ed.) Readings in Philosophy of Psychology. Vol. 1, Cambridge: Harvard University Press.

Dahlbom, Bo (1993) (ed.) Dennett and His Critics. Cambridge: Blackwell Publishers: 184-202.

Dennett, Daniel C. (1991) Consciousness Explained. London: Penguin Books, 1993.

Dennett, Daniel C. (1995) The Unimagined Preposterousness of Zombies: Commentary on Moody, Flanagan, and Polger in Dennett (1998): 171-177.

Dennett, Daniel C. (1998) Brainchildren: Essays on Designing Minds. Cambridge, MA: The MIT Press.

Dennett, Daniel C. (1999) The Zombic Hunch: Extinction of an Intuition? in Dennett (2005): 1-23.

Dennett, Daniel C. (2005) Sweet Dreams. Philosophical Obstacles to a Science of Consciousness.
Cambridge: MIT Press.

Polger, Thomas W. (2000) Zombies Explained in Ross, Brook and Thompson (2000): 259-286.

Rorty, Richard (1993) Holism, Intrinsicality, and the Ambition of Transcendence in Dahlbom (1993): 184-202.

Ross Don, Brook Andrew, Thompson David (Eds.) (2000) Dennett's Philosophy: A Comprehensive Assessment. Cambridge, MA: The MIT Press.