User talk:2001:984:26FC:1:ED40:83DB:4142:3D25

September 2020
Welcome to Wikipedia. We appreciate your contributions, but in one of your recent edits to Proof by contradiction, it appears that you have added original research, which is against Wikipedia's policies. Original research refers to material—such as facts, allegations, ideas, and personal experiences—for which no reliable, published sources exist; it also encompasses combining published sources in a way to imply something that none of them explicitly say. Please be prepared to cite a reliable source for all of your contributions. You can have a look at the tutorial on citing sources. Thank you. Balon Greyjoy (talk) 19:44, 6 September 2020 (UTC)
 * If this is a shared IP address, and you did not make the edits referred to above, consider creating an account for yourself or logging in with an existing account so that you can avoid further irrelevant notices.

2001:984:26FC:1:ED40:83DB:4142:3D25 (talk) 20:12, 6 September 2020 (UTC) (I hope I added this message on the talk page according to protocol...) Thanks for your review. I believe it is an important addition, and may prevent quite some confusion and time loss by readers. I am not the only one who observed this confusion among people who try to get to grips with proof by contradiction in relation to constructive mathematics. I do have another source: this lecture by Andrej Bauer (given at the Institute of Advanced Study): https://www.youtube.com/watch?v=21qPOReu4FI, he mentions what I posted at 2 minutes 20 seconds into the lecture. I think your article would be improved by mentioning this in one way or the other. Bauer even mentions that some mathematicians also call "proving not(P) by deriving a contradiction from P" a "proof by contradiction". (And, of course, this way of proving is accepted by intuitionists, as I mentioned in my addition to the article). This habit of some mathematicians adds to the confusion.