6-43 The conscious computers would be so complex that there would be differences between them.
. . . is disputed by . . .
6-44 Block in the cog.
The claim (Tim Maudlin, 1989)
Computationalism contradicts itself even if we imagine 2 machines
of tremendous complexity running the consciousness program. Imagine
that in this case that both machines allow all the proper counterfactuals.
The second machine, however, has an additional component, a block
suspended mid-air in one of the (never-activated) "counterfactual
gears." This block prevents counterfactual states, and so
the second machine violates the nontriviality condition and is
therefore not conscious. So we have the same contradiction as
before: only one machine is conscious, though by the supervenience
thesis both should be. What's more, it seems odd to claim that
suspending or not suspending a block mid-air in a never-activated
part of the machine should make the difference between a nonconscious
and a conscious machine.
Computationalism still violates the supervenience thesis when we imagine two machines of tremendous complexity, each allowing all the proper counterfactuals, and each running a consciousness program. The second machine has an additional component, a block suspended in mid-air in one of the (never- activated) "counterfactual gears," which blocks any counterfactual states. The two systems manifest identical physical activity, yet the computationalist must declare the first machine conscious and the other (blocked machine) not consciousness because it violates the Non-triviality condition.
The Maudlin argument
Maudlin writes, "Because of the immense quantity of machinery
involved, one might misgive that its removal would necessitate
some considerable change in the physical happenings associated
with the machine. To alleviate such doubts, here are two cases
in which the support can be neutralized by changes that can hardly
be construed as altering the physical activities present.
Maudlin's first case is "An Argument by Addition: Suppose we run Olympia, fully connected, on t [Greek symbol theta] so that (according to the supervenience thesis) the conscious stateo [Greek symbol phi] occurs. Now we reset her (and the tape) to run again, but we add a secondary block to each of the copies of Klara. The second block might be a thin piece of metal suspended between the frozen gear teeth. It need not be in physical contact with any part of the machinery."
Maudlin's second case: "Now, however, were the first block to be removed (which will not, of course, happen when we run Olympia on t [Greek theta] from S[0] to S[n]), the gears would contact the second block and jam. The copies of Klara no longer support the right counterfactuals, so on the second run Olympia is not conscious. But, given that the second blocks in fact never even touch any part of the machinery, exerting no influence or force at all, how could the physical activity taking place in Olympia during the first run be said to differ from that in the second? Speaking loosely, how could the rest of the system know that the blocks are even there?" (T. Maudlin, 1989, p. 425).
References
Maudlin, Tim. 1989. Computation and Consciousness. The Journal
of Philosophy, vol. LXXXVI, no. 8. p407-432.