Derivation of implication in logic
129185
Understanding the truth value for ⇏ when antecedent is false and consequent is true.
140682
Proving a property of a Logic Formal Language
91861
Propositional Logic: p → q, ¬p → r, ¬q → ¬r ⊢ q
141952
Is there a decision procedure for intuitionistic propositional logic?
73231
Why in implication, if premise is false then implication is true?
31299
Using the Fitch system, how do I prove $((p \implies q) \implies p)\implies p$?
113605
In Fitch, how does one prove "(P → Q)" from the premise "(¬P ∨ Q)"?
70166
Why is the universal quantifier $\forall x \in A : P(x)$ defined as $\forall x (x \in A \implies P(x))$ using an implication?
98386
First-order logic and second-order logic confusion
103112
Does the existential quantifier distribute over an implication?
23869
Prove the implication "if $ac>bc$ and $c>0$, then $a>b$" using the contrapositive
158016
Help understanding predicate logic question/proof
45481
Prove or disprove validity: $(\forall x \exists y (P(x) \supset Q(y))) \supset(\exists y \forall x (P (x) \supset Q(y)))$
21035
Clarifying on how if p,q is logically equivalent to p only if q
138897
help with some Hilbert style proofs in a propositional logic axiom system.
72185
The negation of a limit condition, Spivak style.
153440
Is logical implication always determinable from just the given statements?