On a recent long train journey, I read Consciousness: a user’s guide, by Adam Zeman (Yale, 2002), and I cannot recommend it too highly. The author is a neurologist and a teacher of neurologists, with an engaging and lucid prose style. He inclines strongly (as do I) to the belief that physical facts about brains are sufficient to account for consciousness, but without being strident about it; he recognizes that it is very natural for us to feel that there is something mysterious about consciousness.
From his Preface:
I wrote this book partly to satisfy my own curiousity about consciousness, partly because I felt a need for an introduction to the subject which would do justice both to the science and to the philosophy of consciousness, to ‘mechanics’ and to experience. Much of the recent writing about consciousness, some of it brilliant, has been polemical and partial: I have done my best to strike an equitable balance between the warring faction, to chart out the territory and draw a faithful map.
After an initial exploration into the contemporary and historical usage of the word ‘conscious’ and its close relatives, he turns to neurology, providing a detailed but accessible introduction to the structure and activity of neurons and brain structures, with special emphasis on the systems subserving vision. This material can be a bit dry, but the narrative is enlivened by many excursions: into the stages of sleep, into faints, whether induced recreationally or by the large g forces to which fighter pilots are subjected, into ‘opium, alcohol and other anaesthetics’, and especially into those ‘experiments of nature’ where selective damage to the nervous system reveals subtleties that are invisible when everything is working properly: agnosias, neglect, and blindsight, for example.
The book then steps back to look at what evolutionary biology can tell us about neurology and consciousness, and how other mammals stack up compared to humans. The last Part, ‘Consciousness considered’, first surveys a number of grand theories about consciousness coming from the scientific side, and then takes up what historical and contemporary philosophers of mind have to say on the matter.
There is one especially choice passage that I must quote and comment on. In the course of taking up vision there is a subsection headed ‘Recognition’:
Recognition is usually so effortless that we take it for granted. Once in a while a visual mistake startles us from our complacency: a tree trunk on an evening walk looms up like a dark attacker, a twist of black cotton on the floor announces itself as SPIDER. …
A little reflection reveals that such processes are not the exception but the rule. Our knowledge of the world pervades perception: we are always seeking after meaning. … What we see resonates in the memory of what we have seen: new experience always percolates through old, leaving a hint of its flavour as it passes. …
What we see resonates in the memory of what we have seen: this captures, precisely but also poetically, why, in my view, the so-called ‘hard problem of consciousness’ is not a problem at all, even if it will also and forever remain in one sense a mystery. If it is like something to ‘see red’ (in what seems to be the universal canonical example), what it is like is seeing red on thousands of previous occasions.