Mathematical Logic: If I don’t have to show something, why is it always correct?
125317
Is this statement "Every element in the empty set is greater than itself." true or its negation is true?
75600
Is Gödel's modified liar an illogical statement?
42517
Is formal truth in mathematical logic a generalization of everyday, intuitive truth?
72185
The negation of a limit condition, Spivak style.
147947
Does double negation distribute over implication intuitionistically?
88188
Explain proof by contradiction.
59964
Why an inconsistent formal system can prove everything?
150451
Logic soundness and completeness
82739
Why is $\alpha \rightarrow \forall x(\alpha)$ not generally correct in first-order logic?
48761
How can know if a proof technique can actually prove something? Specifically, induction
90473
Is circular reasoning always a fallacy?
73253
Question About equal signs in Theorems
61671
Discrete Math: Writing Proofs
122684
How do you prove Well-Ordering without Mathematical Induction? (and vice-versa)
50178
\qed for theorems without proofs
15504
In classical logic, why is $(p\Rightarrow q)$ True if $p$ is False and $q$ is True?
148790
Basic question about proofs with the goal $\exists x P(x)$