Lucas may be a Turing machine
If we fix up Lucas's argument so that it's more accurate, we discover that it proves something different than Lucas intended. It shows that: Lucas may be a Turing machine—and that, if he is, he has no way of knowing which one he is.
The corrected argument, it turns out, shows that:
- Lucas may be a Turing machine. So Lucas's intended argument—that is not a machine—fails.
- Furthermore, if Lucas is a Turing machine, he has no way of knowing which one he is.
Paul Benacerraf (1967).
Note: This argument Simeon stimulates a highly technical thread of debate that is not represented here because of its length and complexity.
The thread includes papers from Hanson (1971), Chahara (1972), and Reinhardt (1986).