> If you buy into materialism, the idea that the mind arises from the brain through physics alone and nothing else, then your mind is able to be simulated on a big enough computer

Pretty much everyone believes that materialism implies the simulatability of everything physical, but that reality is computable is actually still only a widely held assumption. https://en.wikipedia.org/wiki/Church%E2%80%93Turing%E2%80%93...

We don't know nearly enough about reality to know confidently that it's something you can always simulate.