Given $\exists x.\lnot p(x)$, use the Fitch System to prove $\lnot \forall x.p(x)$
121720
Given ∃x.¬p(x), use the Fitch System to prove ¬∀x.p(x).
37924
Equivalence of norms proof
93410
How to prove ~ (~P & ~Q) : P ∨ Q by natural deduction
84251
Show that $\Gamma \cup \{\neg \phi\}$ is satisfiable if and only if $\Gamma\not \models \phi$
29629
Distinguishing between valid and fallacious arguments (propositional calculus)
151935
Proving the predicate $\forall n \in \mathbb{N} , n \geq 2$ using the Pigeonhole principle
49453
Why do I have to solve for $x$ in this proof, if I choose not to find a counterexample?
93771
Prove that for any set $A$ there is some $x \notin A$
113605
In Fitch, how does one prove "(P → Q)" from the premise "(¬P ∨ Q)"?
83291
Prove that $p(x)=(x-a)q(x)$ for some $q(x)\in R[x]$ of degree= (degree of $p)-1$.
45481
Prove or disprove validity: $(\forall x \exists y (P(x) \supset Q(y))) \supset(\exists y \forall x (P (x) \supset Q(y)))$
151561
Proving 'Law of Excluded Middle' in Fitch system
59187
Proof, is $\forall x : (P(x) \lor Q(x)) \Leftrightarrow \forall x : P(x) \lor \forall x : Q(x)$?
76635
Proof through combinatorial argument
121361
Showing that $\lnot Q \lor (\lnot Q \land R) = \lnot Q$ without a truth table
10540
Prove $\vdash \neg(\square F\land p)$ in $KD$
31299
Using the Fitch system, how do I prove $((p \implies q) \implies p)\implies p$?