Brains in Vats

 Posted by on 9 March 2003 at 10:49 am  Uncategorized
Mar 092003

I’m presently rewatching The Matrix while setting up my new and speedy server. (After setup, hopefully next weekend, I’ll be swapping out this new server for my present old and tired co-located server.)

I was inspired to watch the movie again after listening to David Chalmers’ excellent lecture “The Matrix as Metaphysics” yesterday at Boulder. Chalmers argued that the “Matrix Hypothesis” that “I have (and have always had) a cognitive system that receives its inputs from and sends its outputs to an artificially-designed computer simulation of a world” is not, contrary to our intuitions, a skeptical claim, but rather a metaphysical one. He argues this point by showing that the Matrix Hypothesis is really the conjunction of three non-skeptical metaphysical thesis, namely:

(1) Creation Hypothesis: “Physical space-time and its contents were created by beings outside physical space-time.”

(2) The Computational Hypothesis: “Microphysical processes throughout space-time are constituted by underlying computational processes.”

(3) The Mind-Body Hypothesis: “My mind is (and has always been) constituted by processes outside physical space-time, and receives its perceptual inputs from and sends its outputs to processes in physical space-time.”

So Chalmers writes:

If this [analysis] is right, it follows that the Matrix Hypothesis is not a skeptical hypothesis. If I accept it, I should not infer that the external world does not exist, or that I have no body, or that there are no tables and chairs, or that I am not in Tucson. Rather, I should infer that the physical world is constituted by computations beneath the microphysical level. There are still tables, chairs, and bodies: these are made up fundamentally of bits, and of whatever constitutes these bits. This world was created by other beings, but is still perfectly real. My mind is separate from physical processes, and interacts with them. My mind may not have been created by these beings, and it may not be made up of bits, but it still interacts with these bits.

The result is a complex picture of the fundamental nature of reality. The picture is strange and surprising, perhaps, but it is a picture of a full-blooded external world. If we are in a matrix, this is simply the way that the world is.

What is striking about this whole argument to me is how similar it is to David Kelley’s comments on the brain the vat in his 1987 lecture “Skepticism” from The Foundations of Knowledge. (David Jilk, also at the lecture, noted the strong connection too.) Unfortunately my notes on that lecture were deleted, so I can’t give the details of Kelley’s view. But, if I recall correctly, Kelley argued that the brain in at vat would be aware of reality, but the fundamental constituents of that reality would be different than for brains in skulls. Kelley’s comments in the tape were fairly brief, as he was addressing all four of the major skeptical arguments. But the basic similarity to Chalmers’ argument was as plain as day!

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