Most computationalists default to the Origins of Gravy theory set forth by Walter Matthau in the film of Neil Simon’s The Odd Couple. Challenged to account for the emergence of gravy, Matthau explains that, when you cook a roast, “it comes.” That is basically how consciousness arises too, according to computationalists. It just comes.That's from "The Closing of the Scientific Mind," a piece by Gelernter at Commentary on philosophy of mind and related subjects. I have had my own doubts about brain-as-computer thinking over the years (see here and here, for instance) and expect there will be plenty more contention over this sort of thing in coming years.
UPDATE 1/4: Ronald Bailey has a positive review at Reason of an interesting-sounding book Our Final Invention: Artificial Intelligence and the End of the Human Era by James Barrat. Having not read the book, I don't know if it would convince me I've been wrong to downplay computers-take-over scenarios (I'll admit I've been wrong to downplay computers-take-over-jobs scenarios). In any case, if the technophilia of the libertarian movement gets tempered a bit, I'd see that as a positive development.
UPDATE 1/5: Ordered Barrat's book and will report on it on in due course. Will also be interested in Gelernter's book when that comes out. I am hoping to step up book reviewing here at Quicksilber.
UPDATE 1/10: Good stuff:
UPDATE 1/13: My review of Barrat's book.