Logic · step by step
Natural Deduction
Build your argument. Explore rules, open assumptions and check every step in the same Fitch interface.
System: Classical Propositional Natural DeductionPremises and conclusion
Aliases: ~ for ¬, & for ∧, | for ∨, -> for → and <-> for ↔. Use ⊥ on its own for contradiction.
Local, deterministic computation. The proof remains only in this page’s memory and is lost when you reload or leave.