What it is like
On the axis: The enigma of consciousness · a being's point of view
There is something it is like to be me, and nothing of the sort, presumably, for a stone. But is that "something" one more reality in the world, which physical description lets slip, or only a limit of ours, unable as we are to occupy another's point of view?
This problem is brought out by the thought experiment What is it like to be a bat?:
The bat perceives the world by echolocation: it emits cries and reads in their echoes the shape, distance and motion of things. A biologist can describe that system completely, down to the last neuron. But it would remain to be known what it is, for the bat, to perceive in this way. And we can imagine it only by imagining ourselves as a bat, which is not the same thing: that would be what it is like for a human being to behave as it does, not what it is like for the bat to be itself.
Thomas Nagel, "What Is It Like to Be a Bat?" (1974)
Would a completed science of the bat's brain tell us what it is like to be one?
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Justification
Nagel holds that an organism is conscious if there is something it is like to be that organism, and that this subjective character is tied to a point of view: this is what his stages, in 1974. Every reduction proceeds by moving away from the point of view in order to gain objectivity; applied to experience, the move removes precisely what had to be explained. From this he draws a refusal of , but not a : he maintains that we lack the necessary concepts, and that he cannot see how physicalism could be true, without declaring it false. His 1979 essay examines, without firmly endorsing it, the hypothesis of an intrinsic nature common to the mental and the physical, closer to a neutral monism than to an avowed property dualism; his 2012 book advances another conjecture, that of an oriented tendency inscribed in nature, which he himself offers as speculative.
I want to know what it is like for a bat to be a bat."What Is It Like to Be a Bat?", The Philosophical Review, vol. 83, no. 4 (1974), p. 439
"What Is It Like to Be a Bat?" (1974) · "Panpsychism" (1979) · Mind and Cosmos (2012)
Justification
Chalmers separates the easy problems of consciousness, which concern mechanisms and which science will solve, from the hard problem: why are those mechanisms accompanied by any experience at all? No functional explanation answers it, for describing what a system does leaves untouched what it is like to be one. He concludes that are not reducible to physical processes but are tied to them by laws of nature, and calls his position a naturalistic dualism: consciousness is a fundamental feature of the world, like mass or charge, not a separate substance. He also explores, without adopting it, another route to the same intuition: lodging experience in the intrinsic nature of the physical, of which physics describes only the structure. That option, close to Russellian monism and to panpsychism, remains for him a serious avenue, not the thesis he defends.
"Facing Up to the Problem of Consciousness" (1995) · The Conscious Mind (1996)