Turing's journey
A recent post comments on the value of biography as a source of insight into history and thought. Currently I am reading Andrew Hodges' Alan Turing: The Enigma (1983), which I am finding fascinating both for its portrayal of the evolution of a brilliant and unconventional mathematician as well as the honest efforts Hodges makes to describe Turing's sexual evolution and the tragedy in which it eventuated. Hodges makes a serious effort to give the reader some understanding of Turing's important contributions, including his enormously important "computable numbers" paper. (Here is a nice discussion of computability in the Stanford Encyclopedia of Philosophy ; link .) The book also offers a reasonably technical account of the Enigma code-breaking process. Hilbert's mathematical imagination plays an important role in Turing's development. Hilbert's speculation that all mathematical statements would turn out to be derivable or disprovable turned out to b...