Given p ⇒ q, use the Fitch System to prove ¬q ⇒ ¬p.
To apply a rule of inference, check the lines you wish to use as premises and click the button for the rule of inference. Reiteration allows you to repeat an earlier item. To delete one or more lines from a proof, check the desired lines and click Delete. When entering expressions, use Ascii characters only. Use ~ for ¬; use & for ∧; use | for ∨; use => for ⇒; use <=> for ⇔.
Enter the premise you wish to add to the proof:
Enter the assumption you wish to make:
Enter the conclusion you wish to add to the proof:
Enter the justification for this conclusion:
Enter the sentence you wish to disjoin to the checked items: