First posted 15 April 2006. These days, I tend to think of the brain a lot less when I'm thinking of the mind, but my sense of wonder for whatever it is that is behind our mental experience is undiminished.
Michael O'Shea's The Brain: A Very Short Introduction has shown me that my longstanding wonder with the brain has been understated. You see, I have marvelled at the complexity inherent in a collection of 100 billion neurons - each with a thousand synapses, connections with other neurons - and the effectively uncountable number of possible brain states implied by the permutations of these on-off switches.
O'Shea is also impressed by this, but he adds several other elements of our current understanding that demonstrate that the metaphor of a network of binary electrical switches is far too simple:
All of this suggests that the challenges of 'porting' human intelligence to computer hardware ( a la Ray Kurtzweil) are vastly greater than I had thought. The challenges are similarly greater for efforts such as Dan Lloyd's to eventually map mental states to brain states: the state space, already mind-bogglingly large, is vastly larger still.
It even makes me slightly more sceptical about Julian Barbour's timeless theory of time, because the asynchronous nature of the brain's neuronal (and glial?) interactions doesn't seem to fit well with the notion that particular brain states are but tiny subsets of instantaneous universe states (or Nows) that happily happen to contain records that act as bridges to other Nows. How instantaneous is a Now? If mental states are tied not to instantaneous brain states but are affected by the frequency of repeated neuronal firing, then can a mental state reside within a single Now, given that such a Now, by definition, can contain no change (i.e. no repeated firing)?
But there is a way out. I guess if the brain encodes in each instant information about its state in previous instants (as in discussion of the specious now in Dan Lloyd), then there is no necessary inconsistency between the unquestionable existence of subjective experience and Barbour's theory of time.