Talk:Modus tollens

So... is this a valid proof or valid under certain circumstances or what? Where's the juicy commentary?--Zipperback (talk) 20:01, 4 August 2013 (UTC)

It's always valid. There isn't much to say about it; it's just a rule of logic. Wehpudicabok [話] [変] 20:07, 4 August 2013 (UTC)

I have belatedly updated the article. --Annanoon (talk) 10:55, 1 August 2019 (UTC)