Contrapositive Fitch Proof

Question

I can't seem to figure out how to get past this step. Any suggestions?

I assume you are not permitted to use or do not have modus tollens. https://en.wikipedia.org/wiki/Modus_tollens — Frank Hubeny, Oct 03 '19 at 20:50

score 1 · Answer 1 · answered Oct 03 '19 at 20:58

If you are able to use modus tollens, then the result would follow quickly. Here is an example of that using a different proof checker:

However, if you have to derive this using introduction and elimination rules, the following might work using a proof provided by the authors of forallx (page 170):

Kevin Klement's JavaScript/PHP Fitch-style natural deduction proof editor and checker http://proofs.openlogicproject.org/

P. D. Magnus, Tim Button with additions by J. Robert Loftis remixed and revised by Aaron Thomas-Bolduc, Richard Zach, forallx Calgary Remix: An Introduction to Formal Logic, Fall 2019. http://forallx.openlogicproject.org/forallxyyc.pdf

Thanks so much!! This was very helpful – Grace Oct 05 '19 at 18:44 — Grace, Oct 05 '19 at 18:44

Contrapositive Fitch Proof

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