This is a misunderstanding of the role being played by the zombie argument in considerations of consciousness. The question is whether a zombie world is logically possible (whether it is conceivable), not whether it is coextensive with an epiphenomenalist view of consciousness. That is a critical distinction.
To see the difference, consider the “four-sidedness” of squares. Is it possible to conceive of a world in which squares happen to be other than four-sided? The answer, of course, is no. It would be logically incoherent for someone to ask that we discuss the kinds of universe where this might be possible, because all such discussion would be a waste of time: squares have four sides by definition, so there is no empirical or conceivable fact about any universe that could make it different.
By contrast, we could conceive all kinds of outlandish variations on the physical reality in this universe, and ask questions about those conceptions. We could imagine, for example, a universe in which only the most wise and intelligent people spontaneously rose to the top of all organizations. However bizarre and physically impossible the conception, it is still conceivable … unlike the non-four-sided-square universe.
So the question addressed by the zombie argument is whether a zombie universe is conceivable in that particuar sense. Is a zombie universe logically impossible, for the same kind of reasons that the non-four-sided-square universe is impossible? And if so, on what grounds? Given the terms of the definition of “logically possible” it is meaningless to try to introduce arguments about the contingencies of science, the “deranged” character of a theory that allows zombies to write sincere papers on the subject of consciousness, or the merits of epiphenomenalism, in this context. It is not a question of empirical or theoretical science that makes non-four-sided squares impossible, it is something much deeper, and the question about the zombie world is about whether it too deserves to be categoried as a logical impossibility.
So, the two phrases “consciousness is epiphenomenal” and “zombies are logically possible” cannot be compared: the former is a statement of how consciousness actually plays a role in the universe, whereas the latter is asking about an entirely different KIND of distinction.
For the record, the reason to ask whether zombies are logically possible is that if a thing can be present in the real world, but not present in a logically possible world, it is then meaningful to ask about the nature of the thing that differs between the two cases. That is the goal of positing a zombie world: the goal is not to say that zombie worlds actually do exist, and certainly not to say that zombie worlds are coextensive with epiphenomenalism.
For the record, the reason to ask whether zombies are logically possible is that if a thing can be present in the real world, but not present in a logically possible world, it is then meaningful to ask about the nature of the thing that differs between the two cases.
As long as you’re recording, can you also explain the reason to ask about the nature of the thing that differs between a conscious system in the real world (A) and its logically possible physically identical nonconscious analog in the zombie world (B)?
Relatedly: if it turns out that no such B can exist in the real world even in principle, what depends on the nature of the thing that differs between A and B?
This is a misunderstanding of the role being played by the zombie argument in considerations of consciousness. The question is whether a zombie world is logically possible (whether it is conceivable), not whether it is coextensive with an epiphenomenalist view of consciousness. That is a critical distinction.
To see the difference, consider the “four-sidedness” of squares. Is it possible to conceive of a world in which squares happen to be other than four-sided? The answer, of course, is no. It would be logically incoherent for someone to ask that we discuss the kinds of universe where this might be possible, because all such discussion would be a waste of time: squares have four sides by definition, so there is no empirical or conceivable fact about any universe that could make it different.
By contrast, we could conceive all kinds of outlandish variations on the physical reality in this universe, and ask questions about those conceptions. We could imagine, for example, a universe in which only the most wise and intelligent people spontaneously rose to the top of all organizations. However bizarre and physically impossible the conception, it is still conceivable … unlike the non-four-sided-square universe.
So the question addressed by the zombie argument is whether a zombie universe is conceivable in that particuar sense. Is a zombie universe logically impossible, for the same kind of reasons that the non-four-sided-square universe is impossible? And if so, on what grounds? Given the terms of the definition of “logically possible” it is meaningless to try to introduce arguments about the contingencies of science, the “deranged” character of a theory that allows zombies to write sincere papers on the subject of consciousness, or the merits of epiphenomenalism, in this context. It is not a question of empirical or theoretical science that makes non-four-sided squares impossible, it is something much deeper, and the question about the zombie world is about whether it too deserves to be categoried as a logical impossibility.
So, the two phrases “consciousness is epiphenomenal” and “zombies are logically possible” cannot be compared: the former is a statement of how consciousness actually plays a role in the universe, whereas the latter is asking about an entirely different KIND of distinction.
For the record, the reason to ask whether zombies are logically possible is that if a thing can be present in the real world, but not present in a logically possible world, it is then meaningful to ask about the nature of the thing that differs between the two cases. That is the goal of positing a zombie world: the goal is not to say that zombie worlds actually do exist, and certainly not to say that zombie worlds are coextensive with epiphenomenalism.
As long as you’re recording, can you also explain the reason to ask about the nature of the thing that differs between a conscious system in the real world (A) and its logically possible physically identical nonconscious analog in the zombie world (B)?
Relatedly: if it turns out that no such B can exist in the real world even in principle, what depends on the nature of the thing that differs between A and B?