In the contemporary vocabulary of the philosophy of mind, by zombie (philosophical zombie or p-zombie) is meant a being physically and externally indistinguishable from a conscious being, by his behavior as by his physical constitution, but who, however, has no awareness of his existence or of the world, no feelings or personal experience. Although it behaves as if it is experiencing emotions, the zombie does not experience any, even though the biological and physical processes that determine its behavior are those of a person experiencing emotions.
In its philosophical use, this notion is very far from its current use associated with legend or cinema, insofar as it is stated on principle that a zombie cannot be distinguished from a living and conscious person. Its existence – purely fictitious but logically possible – is postulated only in the context of certain thought experiments intended to show the relevance of body-mind dualism or the insufficiency of physicalism.
It is to George Stout in 1921 that we owe the first description of a world which would later be qualified as a “zombie world”: an imaginary world where the physical processes are identical to ours in such a way that human beings behave and act exactly the same as in reality, except that in this world, human beings are not conscious beings and feel absolutely nothing. However, it was only in the 1970s that this notion emerged following an expression used by Keith Campbell – “imitation man” – to describe a man whose brain states are exactly like ours in their physical properties. -chemicals ”, but which, unlike real humans, does not feel any pain or see any color.
The term “zombie” thus appeared in the context of a debate on the validity of physicalism, and in particular, on the validity of a strong version of physicalism: the theory of mind-brain identity, defended among others by philosophers David Lewis and David Armstrong. The first mention of the word “zombie” in a text that develops the concept was made by Robert Kirk in 1974 in an article entitled: “Zombies vs. Materialists ”.
Principle of indiscernibility
In its philosophical definition, a zombie is a person who behaves in a manner that is indistinguishable from that of a conscious person in light of all possible tests, which includes not only the answers to questions such as those the Turing test, but also psychological, neurophysiological, and all tests that any natural science can design.
David Chalmers, to whom we owe the notion of “zombie twin“, defines his own zombie equivalent (his strictly physical double) as follows:
”So let us consider my zombie twin. This creature is molecule for molecule identical to me, and identical in all the low-level properties postulated by a completed physics, but he lacks conscious experience entirely… He will certainly be identical to me functionally: he will be processing the same sort of information, reacting in a similar way to inputs, with his internal configurations being modified appropriately and with indistinguishable behavior resulting… ”
Although the zombie thus defined is perfectly similar to a conscious being, there is a real difference between a conscious person and his zombie equivalent, since the latter is not conscious. For those who accept the “zombie intuition”, the fundamental weakness affecting any physical theory of consciousness is its failure to account for this crucial difference.
David Chalmers’ zombie
It is to David Chalmers that we owe the updating and development of the “zombie argument”. This argument is advanced by Chalmers to show the insufficiency of explanations in terms of physical processes when they relate to the subjective aspects of consciousness. This is a modal-type argument that relies on what is conceivable or logically possible: a human world physically indistinguishable from our own but where consciousness does not exist is conceivable and therefore logically possible. There is no contradiction to the scenario according to which there exists a universe physically similar to ours in all respects, although the creatures that would be part of it are totally devoid of consciousness.
David Chalmers considers such a scenario to be a pure thought experiment from which no decisive argument can be drawn. But the logical possibility of the zombie shows that facts about consciousness do not logically reduce to physical facts as we understand them and could well be fundamentally different phenomena. If this is the case, and since we know that we are conscious, we should recognize that our world contains more than physical entities of the type of those with mass or electric charge for example: it also includes non-physical consciousness, or else a physical consciousness but understood in a different sense than that given by the current physical sciences.
Because no physical theory accounts for the logical possibility of the zombie, David Chalmers calls for a “fundamental theory” of consciousness from which one could decisively conclude that zombies are physically impossible. According to him, there is a fundamental law of nature, yet to be discovered, which associates conscious experiences with the functional organization of the brain such that a brain that functions like ours cannot be that of a zombie. In an imaginary but logically possible world called “zombie world”, this law does not exist, although all the other laws of nature exist.