Question: Was Turing an idealist?
Based on Turing's work and writings, it seems that he was not an idealist in the philosophical sense, which holds that reality is ultimately mental or spiritual in nature. Instead, he was a materialist who believed that the mind and consciousness could be explained in terms of physical processes.
In his 1950 paper "Computing Machinery and Intelligence," Turing famously proposed what is now known as the Turing Test, a way of evaluating a machine's ability to exhibit intelligent behavior that is indistinguishable from that of a human. The paper suggests that intelligence is not a mystical or spiritual quality, but rather a product of computation and algorithmic processes.
Similarly, in his 1952 paper "The Chemical Basis of Morphogenesis," Turing explored the idea that biological development could be explained in terms of chemical reactions and physical processes, rather than divine intervention or mystical forces.
Overall, based on his work and writings, it seems unlikely that Turing would have been characterized as an idealist in the philosophical sense. However, as with any complex historical figure, there may be nuances and subtleties to his beliefs that are not captured by a simple label.
Question: Did Turing believe in the Church-Turing thesis?
Yes, Alan Turing is known to have strongly believed in the Church-Turing thesis and played a key role in formulating and popularizing it. In his seminal 1936 paper "On Computable Numbers, with an Application to the Entscheidungsproblem," Turing introduced the concept of a Turing machine as a theoretical model of computation and argued that it could be used to capture the notion of an algorithmic procedure.
Turing's work on the theory of computation helped to establish the Church-Turing thesis as a fundamental concept in theoretical computer science and mathematical logic. He is often credited with laying the foundation for the development of modern computer science and his contributions to the field continue to be celebrated and studied today.