AE,
Cars are unproblematically physical objects, they are made of matter and their powers all derive from the powers of their constituents. But a car is not identical with its matter. Disassemble it or melt it down and you no longer have a car. But replace each piece of the car gradually, and arguably you have the same car. Try to describe the laws of auto-mechanics in purely physical terms, and you have a problem, because cars can be realized in multiple materials. From the engineer's point of view, a Ford Taurus made of metal and one made of hard plastics whose physical properties approximated metal would be very slight -- the same laws of automechanics would apply. But from a purely physical point of view, the difference between two cars will seem vast.
Cars and the laws of auto mechanics emerge at a level above that of particle physics, yet there is surely nothing mysterious about this emergence -- since as I said, the powers that cars have can be fully explained in terms of the powers of their constituents when those constituents are organized in a certain way (though they are not identical with those constituents).
In the case of life, I believe we are also able to see the emergence of life from the matter that makes it up as non-mysterious. The operation of DNA is well understood at a chemical level -- no extra vital force enters into the replication of DNA or in DNA's synthesis of proteins. And once you have a self-replicating complex molecule like DNA, natural selection explains how eyes and wings, birds and humans could arise without the intervention of any non-physical forces or beings.
Consciousness is a far more difficult matter. In my view, Daniel Dennet's title "Consciousness Explained" is very premature. Still, the dualist who would erect an explanatory wall between human consciousness and the rest of the world has a problem too: animal consciousness. Which side of the wall does it go on? Descartes consistently denies that animals have consciousness, but this is just obviously false. We seem to face something of a continuum of consciousness among animals -- if there is a dualist wall between matter and consciousness, where does it go?
In any case, I think the desire to erect walls is premature. I think the existence of minds (and of moral truths for that matter) is as clear as the existence of physical objects. A science that dismisses mind seems to be undercutting its own basis in experience. Physics has to find a way to leave room for the existence of minds and for the manifestations of mind we see in the world, or it will be undercutting itself. Just as physics seems to put some constraints on psychology, so psychology puts constraints on physics. Until we have a theory that reconciles physics and psychology, we should go on with both -- as physicisst themselves go on with Relativity and Quantum theory, even though the two cannot be employed together (unless superstring theory turns out to reconcile them).
[This message has been edited by ChrisW (edited April 18, 2004).]
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