Proving that a sentence is inconsistent
10540
Prove $\vdash \neg(\square F\land p)$ in $KD$
106234
Notes on Sentences
150291
On what grounds does one determine the grammatical acceptability of a sentence fragment group?
65651
Facts in reported speech – to backshift or not
136584
Understanding connection between terms tautology, contradiction, contingent, satisfiable, unsatisfiable, valid and invalid
104626
Undecidable language problems.
109858
How could a statement be true without proof?
56325
If we accept a false statement, can we prove anything?
17299
Conditional sentences not starting with "if"
61671
Discrete Math: Writing Proofs
113957
Why is it possible to conclude everything from a false statement?
3979
Limit comparison test proof
53199
First-Order Logic: Formalisation of the phrase "Not all that glitters is gold"
150041
T must be contravariantly valid
1508
How do I prove that a definition of an ordered pair does not satisfy the required property?
6166
Is the following statement provable?
136577
In formal logic, how is it possible for an argument with a contradictory conclusion to be valid?