Friday, November 23, 2007

Art, Science & Truth: Deep Nonsense

Art, Science & Truth: Jonah Lehrer: Reading Jonah Lehrer's Proust Was a Neuroscientist is something like watching Jacoby Ellsbury in the Red Sox outfield. [... ] Lehrer's stylish little book is a brief for art in an age of science. He stands with artists, for starters, because as he argues in eight signal lives, they hit the target first, about brain science in particular: poet Walt Whitman's intuition of "the body electric," for example; or novelist George Eliot's confrontation with systems thinking (Herbert Spencer, in person, and the invented Casaubon in Middlemarch) and her elevation of the indeterminacy of real life; or Paul Cezanne's methodical discovery of our eye's part (and our imagination's) in completing the experience of a painting. [...]

Scientists describe our brain in terms of its physical details; they say we are nothing but a loom of electrical cells and synaptic spaces. What science forgets is that this isn't how we experience the world. (We feel like the ghost, not like the machine.) It is ironic but true: the one reality science cannot reduce is the only reality we will ever know. This is why we need art. By expressing our actual experience, the artist reminds us that our science is incomplete, that no map of matter will ever explain the immateriality of our consciousness.
Jonah Lehrer, Proust Was a Neuroscientist, page xii.
(Via Open Source.)

I listened to this podcast at the gym today. I must have worked out harder to burn off the irritation with so much flim-flam. Science is Chris Lydon's weakest area by far. He's too willing to accept mystical pieties from his subjects that he would probe sharply in an interview about Iraq or Emerson.

Proust and Musil supplied important places away from my research when I was in graduate school. Reading À la Recherche du Temps Perdu in the original required such concentration that the difficulties with my work were erased for a while. But neither Proust nor Musil were really outside my most serious research concerns. Proust on Elstir or Musil on Moosbrugger raised tantalizing questions about perception, consciousness, and free will. So I was ready to be sympathetic towards Lehrer's book, which was in my “to read” list. No more.

In the interview, Lehrer talks in hushed tones about the “essential mystery” of individual experience that cognitive science will “never” answer. Lydon seems almost relieved that there's some mystical core left after all.

Lydon doesn't realize that Lehrer's mystery is trivial, a result of confusion between the particular and the general.

What cognitive science seeks is a general account of cognitive mechanisms. What art provides are particular accounts of experience, valuable exactly because of their particularity. A general account of cognitive processes cannot predict particulars any more than the logic diagram for this Intel Core Duo can predict what instruction will execute next. That instruction is determined by a combination of the processor, the contents of memory, and events in the outside, like the keys I tap and the packets that arrive on the net interface.

Even if we had a complete wiring diagram of someone's brain, we could not predict the next neuron firings, let alone the next action of the subject, because we don't know the contents of memory, encoded in the states of synapses and of individual neurons (such as feedback-stabilized patterns of gene expression), nor what particular sensory events will happen next.

More generally, Lehrer seems to be totally oblivious to the huge 20th century discovery that unpredictability is the rule for sufficiently powerful computing devices. The unsolvability of the halting problem is just the most extreme case of unpredictability: no general method can predict in finite time whether an arbitrary program will halt. A good pseudo-random number generator is unpredictable if we do not know its seed. Thinking of individual experience as a unique bit stream, it is not surprising that individual behavior is so unpredictable: we all have different seeds. In addition, cryptographic arguments show that a combinatorial circuit of sufficient complexity cannot be reconstructed from a polynomially-sized sample input-output behavior.

If Lehrer wanted to puzzle over a real question that matters in this argument, he could have asked about our current lack of proof for the cryptographic assumptions used in the above argument. Now, there's a mystery. Not an “essential” one, we hope, but certainly a resistant one.

It is somewhat depressing that even highly educated people like Lehrer are so ignorant of the amazing discoveries on the limits of computation since 1936, and what they may imply for our understanding of the mind; and that they seem ready to go all weak at the knees with mystical copouts as soon as the opportunity presents itself.

To admire Proust or Musil I need no mystery: it is enough that they could create compelling experiences that illuminate the uniqueness and weirdness is all of us, which will stand however much we know about brains and minds, not because of any mystery, but because computation has limits. Unpredictability makes us free.

Update: Complementary claims of nonsense.


Venu said...

"In addition, cryptographic arguments show that a combinatorial circuit of sufficient complexity cannot be reconstructed from a polynomially-sized sample input-output behavior."

Could you point me to any references on this?

Fernando Pereira said...

Cryptographic Limitations on Learning Boolean Formulae and Finite Automata. M.Kearns and L. Valiant. Journal of the ACM 41(1), pp. 67-95, 1994, and many follow-up papers.