Brain game

There’s no physical evidence of human consciousness, so what is it? A neuroscientist shares 19 theories.

- DANYL MCLAUCHLAN

NINETEEN WAYS OF LOOKING AT CONSCIOUSNESS, by Patrick House
(Hachette, $37.99)

In a written sentence, where do the words end and the sentence begin? The neuroscientist Patrick House wonders if the question is relevant to the problem of consciousness.

Our brains resemble salty, watery walnuts about the size of two clenched fists. They have folds and crevices; the surface bulges and shrinks in time with our heartbeat. The organ’s purpose is to take in sensory data from the body, build statistical simulations of both the body and the environment around it, then issue commands in response to predictions generated by the simulations.

All of these functions are understood, to a greater or lesser degree, but the brain also generates consciousness: the sense of being a self-existing inside those simulations, of seeing and feeling and thinking and doing. No one has the slightest idea of how it does this. Physicists can probe the interior of an atom and land spacecraft on another planet, House complains, but biologists don’t know what sadness is. If we didn’t experience consciousness ourselves we’d have no way of knowing it existed in the universe: there’s simply no physical evidence for it.