Exactly! A very nice explanation of what is and what is not a proof by contradiction is given by R. Harper in "Proofs by contradiction, versus contradiction pro

Exactly! A very nice explanation of what is and what is not a proof by contradiction is given by R. Harper in "Proofs by contradiction, versus contradiction proofs" [1] - [1] "https://existentialtype.wordpress.com/2017/03/04/a-proof-by-contradiction-is-not-a-proof-that-derives-a-contradiction/ https://existentialtype.wordpress.com/2017/03/04/a-proof-by-...