X-Message-Number: 7900 Date: Thu, 20 Mar 1997 08:28:19 -0800 (PST) From: Joseph Strout <> Subject: functional equivalence ==> same consciousness OK, I haven't had time to dig up the Chalmers reference, but since there seems to be much interest in it, I'll reconstruct it from memory. This is the demonstration that two functionally equivalent systems must have the same conscious experience. Suppose we have made an artificial visual cortex which is functionally equivalent to your own. Regardless of what it's made of, it will give the same outputs for any set of inputs as your normal, biological cortex. We cleverly hook this up to the rest of your brain via a switchbox: with the switch in one position, your bioligical visual cortex is engaged, and in the other position, the artificial cortex is used instead. With your biological cortex engaged, we show you a red apple and ask you what color you are experiencing. "Red," you say. Then we throw the switch, engaging the artficial cortex. Now, suppose that this artificial cortex generates different qualia -- for example, it causes an experience of blueness in place of redness, and vice versa. So you are now seeing a blue apple. But the cortex is functionally equivalent, so it must generate the same outputs to the rest of your brain (and eventually to the muscles of your mouth and tongue). So though you are experiencing blue, when we ask what you see, you must say "red". As we flip the switch back and forth, you must always say that you see only red and have seen nothing but red. Assuming the artificial cortex does not somehow make you into a liar, this is absurd -- why would you be forced to say you see red when actually you see blue? Our supposition must be false; and this was that the artificial cortex generates different qualia than the biological cortex. Therefore, it must be that functionally equivalent artificial cortex generates the *same* qualia. (We argued here using qualia different in kind, but you could make an analogous argument for no qualia at all.) The example was simplified by restricting it to just some cortex. But surely if having *some* artificial cortex generates the same conscious experience, then having more of it will not suddenly make your qualia disappear. So any artificial brain -- provided it is functionally equivalent -- will have the same conscious experience as the original. Note, too, that we are NOT assuming what we want to prove here. Functional equivalence is a well-defined and relatively weak property, namely, that the input-output relation is the same. It says nothing about what goes on inside; could be ions moving through lipid membranes, or electrons moving through transistors, or speedy little elves shuffling around pieces of paper. Some of these systems, of course, will be impossible to build. Thomas believes that no symbol-manipulation system could feel like us, so in essence, he is asserting that such a machine could not be functionally equivalent. Bob goes farther, suggesting that perhaps no machine made out of nonbiological materials could be functionally equivalent to our brain. Could be true (though I have seen no evidence for it). But at least we should be able to agree that if some machine IS functionally equivalent to another, then their conscious experience is the same. ,------------------------------------------------------------------. | Joseph J. Strout Department of Neuroscience, UCSD | | http://www-acs.ucsd.edu/~jstrout/ | `------------------------------------------------------------------' Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=7900