Turing used a metaphor that was appropriate to his time: a tape, an alphabet, and a machine that reads (and writes to) the tape. It is a simplified expression o

Turing used a metaphor that was appropriate to his time: a tape, an alphabet, and a machine that reads (and writes to) the tape. It is a simplified expression of real machines - but it does not capture the essence of the connection between physics and computer science, because it does not stress the core features of what are required for computation physically, and only presents a simple isomorphism for reasoning about any given computational machinery. Actually, it had been a while since I read "Computing Machinery and Intelligence" and he does, in fact, speak directly to these issues (distinguishability of states, support for N distinct states not just 2) in sections 3 and 5 [1]. And in fact he notes the arbitrariness of the "tape" formulation. I think my point remains, though, that "The Turing Machine" itself does NOT stress these points, picking only advantageously simple examples of distinguishable states, even if the paper does. 1 - https://redirect.cs.umbc.edu/courses/471/papers/turing.pdf https://redirect.cs.umbc.edu/courses/471/papers/turing.pdf