Why is it sensical for a proposition with a false antecedent to validate to true?
578
In classical logic, why is $(p\Rightarrow q)$ True if both $p$ and $q$ are False?
1027
Why is this true? $(\exists x)(P(x) \Rightarrow (\forall y) P(y))$
119888
Is it possible to convert $\forall$ quantifiers to $\exists$ quantifiers without negation?
122015
"This statement is false" - Propositional Logic
17078
if(false==condition). Why?
136734
Do truth tables need proofs?
141179
‘It’ – ambiguous antecedent?
104588
What's the term for denying something so as to raise doubt?
42590
Understanding implication in logic truth tables (excerpt from textbook)
144129
Is it okay to dispute the premise of a question?
125317
Is this statement "Every element in the empty set is greater than itself." true or its negation is true?
143627
Use the Fitch system to prove the tautology (p ∨ ¬p)
136584
Understanding connection between terms tautology, contradiction, contingent, satisfiable, unsatisfiable, valid and invalid
146188
Why does a proof of $\exists f: X\to Y$ injection $\iff \exists g: Y \to X$ surjection requires the axiom of choice?
105303
'Obvious' theorems that are actually false
136577
In formal logic, how is it possible for an argument with a contradictory conclusion to be valid?
144060
Why does this formulation of Choice not follow from the Comprehension Schema?