In the literature of the philosophy of mind, there is what writers refer to as the "hard problem." The premise of this problem is this: suppose that we explain all the functions and causes of human behavior and conscious states. There will still remain the issue of why the human being has to be conscious in order to perform these functions and be affected by these causes. The task of explaining the functions and causes is called the "soft problem." The task of explaining why there has to be consciousness in the first place is the "hard problem."
The Turing Test is a major influence behind the rise of the hard problem. In the Turing Test, whether the chat message is generated by a non-conscious computer or by a conscious human agent makes no difference. What the Turing Test shows is that one does not have to have
consciousness in order to interact with another human being and convince
the other that one is intelligent. (I ignore Searle's Chinese Room argument here as it only begs the question.)
Therefore, in order to tackle the hard problem, a good place to start is to ask whether the Turing Test really does work without consciousness. The answer must be immediately obvious: no, it doesn't. Sure, the system which produces the chat message does not have to have consciousness. However, the chat message is seen as the product of an intelligent being because the judge or subject has consciousness. This suggests that in the case of human intelligence, Berkeley's esse est percipi does hold. Intelligence can exist only in so far as it is for consciousness, or related essentially to consciousness.
The above criticism works against a position which maintains that intelligence-like behavior is in itself sufficient to count as intelligence, and so intelligence can exist without consciousness. However, the criticism does not yet hold against an extreme form of what philosophers call "physicalism." "Physicalism" states that a complete account of "physical facts" is at the same time a complete account of all the properties which exist in the world. Consciousness is just one way in which a property of the world becomes manifest. Therefore, things can be the way they are without necessarily being manifested as consciousness. The hard problem raises its head again here from a new angle.
In Mind Time, Benjamin Libet cautions that physicalism is only a hypothesis. Here I agree with Libet. Physicalism arbitrarily introduces the old-fashioned distinction between appearance and reality, and ascribes reality only to a certain range of phenomena. This is arbitrary, for neither experimental evidence nor the concepts of the "hard sciences" give support to this claim. Here, it is also good to remember that even physicists do not believe that only those things studied in physics really exist and everything else is just a manifestation of it. When physicists such as, say, Richard Feynman, speaks of chemistry as being "reducible" to physics, he is only talking about the possibility of translating the accounts given in chemistry into accounts given in physics. Such a translation already presupposes that both the chemical and the physical exist. Likewise, an organism is not metaphysically "reducible" to chemical phenomena. Biology does rely on chemistry extensively, but again, the way in which this reliance is determined depends on biological facts, not chemical facts. The same can be said of consciousness and the mind. The action of the mind can be translated into a series of biological facts, but the biological account cannot account for why such facts transpire the way it does specifically. For example, the secretion and reception of oxytocin might be one way of describing the phenomenon of breast-feeding, but without the goal of feeding the infant, the purely chemical and biological account cannot explain why there is a link between oxytocin and breast-feeding in the first place.
In my view, the appeal of physicalism comes from the philosophers' mistaken overestimation of what physics, chemistry, and biology can offer. In so far as actuality is concerned, there is no reason to believe that such a thing as a "complete account of the world" which leaves out consciousness is even possible.
If we accept that physicalism is at best only a thought experiment, then the hard problem vanishes. This is not to say that physicalism is a worthless thought experiment. Quite the contrary, I would argue that it is a necessary thought experiment for getting clear on the distinction between consciousness and the lower natural phenomena. The mistake of physicalism is that it assume that a complete "physical" account of the world is actually achievable even if consciousness exists.
