On the Contrary

I have just finished reading through On the Contrary, a collection of philosophical essays on neuroscience. For me, the main interest in this work is understanding how society perceives the social and philosophical implications of neuroscience. I can recommend the text, particularly section II : "Meaning, Qualia, and Emotion" for anyone wanting to become acquainted with how advances in neuroscience have impacted the philosophy of consciousness and free will.

Chapter 13, by Rick Grush and Patricia S. Churchland, in particular amused me. This is a critique of Sir Roger Penrose's quantum consciousness hypothesis. Some of Penrose's speculations have gained foothold with those ignorant of neuroscience and physics, and it may be reasonable to point readers tempted by Penrose's speculations to this chapter, to slow the spread of misinformation.

My spin on this is that Penrose's hypothesis stems from an inexact understanding of computational complexity. Penrose believes that the human brain can solve problems that can only be solved by quantum computers. As I understand it, we do not yet completely understand what quantum computing buys us in terms of computational power. It seems to me that we have not adequately explored the limits of approximation algorithms with access to randomness to say whether classical physics can support cognition. Penrose invokes quantum computation to resolve speculative limits on classical computation, and looks for a quantum soul at the edges of scientific ignorance. I do not think Penrose has adequately motivate these claims with computational complexity, and the mechanisms he proposes -- quantum effects in microtubules, are so speculative that falsifying them is low priority for serious neuroscientists and physicists.

I side with the authors of this chapter: quantum consciousness is, at present, wishful thinking, motivated by the hunch that cognition is "magical", and so must depend on the only branch of physics which holds equal mystery : quantum physics. All reasoning after this is a series of speculations reminiscent of Descartes' speculation on the pineal gland. This critique of Penrose reminds me of the end of Exit Through the Gift Shop, wherein Banksy admits that, perhaps, there are some people who just ... should not do art. "I mean I always used to encourage everyone I met to make art, I used to think everyone should do it. I don't do that so much anymore". I'm afraid Penrose's quantum brain hypothesis is of a similar character : success in some scientific fields does not immediately qualify you to theorize in others.