Because the people who study computations don't know how to instantiate any other type of computation in the physical world. So that any OTHER type of computation may well exist; but it has not yet been discovered. You're just talking about a hypothetical future leap in technology; but you THINK you are saying something much more tangible than that. You're not. You're making an unjustified leap. The science isn't there. Yes you can CALL the secret sauce of consciousness a "computation." And you can say that you mean it in a sense more general than just a TM. The problem is -- you haven't got such a thing. Nobody does. The point isn't to deny there could be a mode of computation that's not a Turing machine. It's that nobody's ever found an example of such. The rest of your post was interesting. I would love to respond point by point. But having reread my own previous post, I think it came out pretty well and I'm content to let that post stand as my thesis. With more words I could only repeat what I've said. I'm going to take a break from this very interesting thread for a while. The conversation has helped me to clarify some of my own thoughts about these matters. Thanks to everyone who chatted. This has been a thoughtful thread.