FOM: relevance and v-Elim

[Vladimir Sazonov]

A small addition to discussion by Jon Barwise and Neil Tennant on 
"the rule of v-Elim (proof by cases) so that if one case leads
to absurdity then the conclusion of the other case can be brought down
as the main conclusion". 

I use this natural rule in lectures for students to show that 
(A=>B) <=> (~AVB) and that (falsity=>anything) because direct 
postulating these lows of classical logic seems rather artificial 
for the beginners. 


Vladimir Sazonov