Thanks, that's a nice quote. I had read that text as a student, but overlooked this morsel. I wonder if Frege's older Begriffsschrift (1879) doesn't already di

Thanks, that's a nice quote. I had read that text as a student, but overlooked this morsel. I wonder if Frege's older Begriffsschrift (1879) doesn't already discuss, or at least mention, higher-order functions. After all, in this text Frege explains his new conception of function. I also wonder if Cantor would have been aware that this is possible.