There is something which always made me uncomfortable with informal proof by contradiction (by informal I mean "with pen and paper"). So OK we reach a contradiction, and then immediately "oh yeah, that is _this hypothesis_ which is wrong". Erh, well why exactly this one? All we know is we started from an inconsistent state.
The article enters this territory at the last paragraph and simply concludes "This can be difficult questions to resolve to student's satisfaction", without even trying to answer it.
The article enters this territory at the last paragraph and simply concludes "This can be difficult questions to resolve to student's satisfaction", without even trying to answer it.