Turing's thesis claims that each function which can be
computed by humans according to an explicitlydescribed procedure is a
function defined by a Turing machine. Turing's thesis stands as an
established empirical principle, having withstood many tests to its
validity. But can Turing's thesis be derived from a more fundamental
physical principle? For example, is it a consequence of the laws of
physics? We survey historical attempts to formulate such a physical
principle, noting that many of the attempts are special cases of a more
general, unified thesis.
