Hey guys I’ve been stuck on deriving Dodec(f) from Small(e). It seem simple but I can’t figure it out. I’ve already derived Dodec(f) from ¬Dodec(e) and Dodec(f).

Thanks for your help.

Hey guys I’ve been stuck on deriving Dodec(f) from Small(e). It seem simple but I can’t figure it out. I’ve already derived Dodec(f) from ¬Dodec(e) and Dodec(f).

Thanks for your help.

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Alexander OttenbergHi Carlos,

I was stuck on this one for a while too…

I’d echo what both Nate and Liz were suggesting. Experiment with Tarski’s for a while, I only used Fitch at first too.

Best,

Xan

Elizabeth SheedyHi Carlos,

Something that really helped me with 6.11 is trying both Fitch and Tarski‘s World to determine whether the argument is valid. Tarski‘s World ended up working for me after experimenting with blocks e and f.

Sincerely,

Liz

Carlos SerranoPost authorHey Liz,

I used Tarski’s World and its definitely valid. I just don’t know what steps to take in Fitch to show that.

Nathan MacDonaldHi Carlos,

If you determine that the proof is not valid (that is, there is a way for the conclusion to be false when all of the premises are true), then you only need to build a counter example using Tarski’s world and you don’t need to use Fitch. I recommend you experiment with worlds where the conclusion is false but all the premises are true.

Best,

Nate