Talk:False premise

"The streets are wet only after it has rained" seems to be an invalid premise to me, since it takes the form of "if and only if", which dosen't apply to this scenario.

Homophobic?
In the statement "The cowboy is neither homosexual nor female, therefore he is not a lesbian.", premise 1 (the cowboy is not female) and premise 2 (the cowboy is not homosexual) might both be false. The cowboy would very well be a homosexual female or at least (if kept to the strict wording of cowBOY) - a homosexual male. Now THAT's an awkward situation, heh? Misiu mp (talk) 16:58, 23 November 2011 (UTC)
 * He's a cowBOY, as you yourself note, therefore not female, and he spends all day thinking about women (implied by the joke), therefore not a homosexual male. The premises (not the premises in question, btw) are taken directly from the story. The false premise in this case is that only lesbians think about women all day.--98.119.17.9 (talk) 03:34, 30 April 2013 (UTC)

IMO this is a poor choice of example. Had a more straightforward example been chosen, one would not need enter any discussions on whether the joke might be offensive to some or not. 82.27.201.132 (talk) 23:38, 30 June 2014 (UTC)

It's also an unnecessary example. It introduces itself to show that a false premise "can also be a premise that is poorly or incompletely defined", but that's already what's happening in the wet streets example (where "if the streets are wet it has rained recently" is the same as "if you think about women you are a lesbian"). --Gnomus (talk) 08:30, 1 June 2015 (UTC)

Contradiction to F->F being Valid?
I get the fact that false premises with false conclusions are valid but unsound. Consider the following example:


 * "If Shape A is a square, then Shape A is a rectangle." - in case Shape A is a circle, this would make the premise and conclusion both false but valid.

However, imagine this example:


 * "If Shape A is a circle, then it has corners." - In case Shape A is an oval, this would make it F->F but certainly not valid had Shape A been a circle. This would also be the case with an F->T scenario (e.g. if Shape A had corners, like a rectangle).

Any thoughts? Cornelius (talk) 03:13, 9 August 2017 (UTC)


 * Answered my own question: the logic has to follow deductively from the premises. Cornelius (talk) 03:25, 9 August 2017 (UTC)