Why is "an invalid argument, the conclusion of which is a tautology" not possible?
109685
An invalid argument, the conclusion of which is a tautology
150053
Is "$(P \land Q) \to P$" a tautology?
143627
Use the Fitch system to prove the tautology (p ∨ ¬p)
136577
In formal logic, how is it possible for an argument with a contradictory conclusion to be valid?
143318
Is it possible to accept the alternative hypothesis?
59964
Why an inconsistent formal system can prove everything?
135957
Why in an inconsistent axiom system every statement is true? (For Dummies)
45481
Prove or disprove validity: $(\forall x \exists y (P(x) \supset Q(y))) \supset(\exists y \forall x (P (x) \supset Q(y)))$
24480
Can there be true conclusions without assumptions?
88566
Is denying "Paradoxical Partitioning" equivalent to accepting the Axiom of Choice?
100399
A doubt with a part of a certain proof.
98537
What is wrong with the proof?
74875
Do we know if there exist true mathematical statements that can not be proven?
12186
How does predicate logic handle contradictory statements about something that does not exist?
113605
In Fitch, how does one prove "(P → Q)" from the premise "(¬P ∨ Q)"?
43655
Verify is tautology by using logical equivalence
51877
Why is this 'Proof' by induction not valid?