New posts in Natural Deduction

$\vdash (\lnot \chi \to \lnot \theta) \to (\theta \to \chi) $

How to derive ~(P → Q) → P?

Is this a correct natural deduction proof?

Is law of excluded middle necessary in this proof?

On the reiteration (or repetition) rule in natural deduction: is the rule "obvious" or does it need a proof?

Everyone loves all lovers, Romeo loves Juliet $\vdash$ I love you (Natural deduction proof)

Solving a Smullyan style knight and knave problem using natural deduction. How to shorten this proof?

Conditional Proof with Conditional within Antecedent

Prove $\neg (p \land q) \vdash \neg p \lor \neg q$ by natural deduction

Natural Deduction Proof for Modus Tollens