My apologies, I was imprecise in my original comment. I was trying to get at the fact that “whether Turing machine M halts” is not actually a concrete question, as had been claimed above (I was assuming that the reason it was presumed to be concrete is because you can just watch the machine and it either halts or doesn’t, and my point was that you can’t actually just watch a machine to see if it will halt).
My apologies, I was imprecise in my original comment. I was trying to get at the fact that “whether Turing machine M halts” is not actually a concrete question, as had been claimed above (I was assuming that the reason it was presumed to be concrete is because you can just watch the machine and it either halts or doesn’t, and my point was that you can’t actually just watch a machine to see if it will halt).