Natural Deduction - helpful links, tutorials, and stuff

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Natural Deduction - helpful links, tutorials, and stuff
Hey people,
I don’t know if you all struggle with ND as much as I do. But I thought we could share some links, tutorials, videos or descriptions on how to do this. So we all master the technique :wink:

I found this video: The guy is strange, but the explanations help a lot I think. There are more videos about how to do Fitch style ND on his channel.

Please tell me if you found other interesting or helpful things.


I found that it was very very helpful for me to do the proofs of some basic logic concepts first, namely:

  • Modus ponens: (( p → q ) & p ) → q
  • Modus tollens; (( p → q ) & -q ) → -p
  • Hypothetical syllogism: (( p → q ) & ( q → r )) → ( p → r )
  • Disjunctive Syllogism: (( p | q ) & -p ) → q
  • Addition: p → ( p & q )
  • Comoposition: (( p → q ) & ( p → r )) → ( p → ( q & r ))

There are many more that you can find on the internet. The big aha came when I figured that I could use these proofs in other proofs. And then suddenly everything felt pretty easy.

Thank you very much luzi, they helped me as well! I think in the addition rule it should state (p v q) instead of (p & q). Gave me quite a cold sweat how to proof it until I found the “rule of addition” online :smiley:

oh yes that is correct indeed. Sorry. You can find more formulas here

I’m searching for nice PL1 ND problems to get used to that too.