Logics; Proof by contradiction (specific question)
22193
Why, logically, is proof by contradiction valid?
75381
How can we reason about "if P then Q" or "P only if Q" statements in propositional logic?
41318
Can every proof by contradiction also be shown without contradiction?
75387
A proof that $1=2$. May I know why it’s false?
134120
Prove statement with a counter-example: For all sets S, T and V, V ∪ (S ∩ T) = (V ∪ S) ∩ T is false
66948
Proving question on sets
68607
Could an argument with false Premises and a true Conclusion be logically valid?
88188
Explain proof by contradiction.
76635
Proof through combinatorial argument
98386
First-order logic and second-order logic confusion
138897
help with some Hilbert style proofs in a propositional logic axiom system.
13074
Prove Logical Equivalence
52322
Implication in mathematics - How can A imply B when A is False?
155679
If union of two theories is not consistent one of them implies a sentence which the other implies opposite of it
136584
Understanding connection between terms tautology, contradiction, contingent, satisfiable, unsatisfiable, valid and invalid
29110
Propositional Intuitionistic Logic Question
93557
Intuitively, why does (B → S) ≡ (¬B ∨ S)?