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cousin_it comments on Open thread, Aug. 03 - Aug. 09, 2015 - Less Wrong Discussion
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Yeah, that's probably right. I'm not sure what "logically possible" means to philosophers, so I tried to give a reductio ad absurdum of the argument as a whole, which should work for any meaning of "logically possible".
Logically possible just means that "it works in theory" -- that there is no logical contradiction. It is possible to have an idea that is logically possible but not physically possible, e.g., a physicist might come up with a internally consistent theory of a universe that hold that the speed of light in a vacuum is 3mph.
These are in contrast to logically impossible worlds, the classic example being a world that contains both an unstoppable force and an unmovable object; these elements contradict each other, so cannot both occur in the same universe.
OK.
Is a world with Newtonian gravity and non-elliptical orbits logically possible?
Is a world where PA proves ¬Con(PA) logically possible?
Is a world with p-zombies logically possible?
Too often, people confuse "I couldn't find a contradiction in 5 minutes" with "there's provably no contradiction, no matter how long you look". The former is what philosophers seem to use routinely, while the latter is a very high standard. For example, our familiar axioms about the natural numbers provably cannot meet that standard, due to the incompleteness theorems. I'd be very surprised if Chalmers had an argument that showed p-zombies are logically possible in the latter sense.
This is shorthand for "in the two decades that Chalmers has been working on this problem, he has been defending the argument that..." You might look at his arguments and find them lacking, but he has spent much longer than five minutes on the problem.