Propositional Logic | Symbolic Logic Tutorial | Attic Philosophy

[@KudaIzka]

I always enjoy watching logic videos, no matter who is teaching. Thanks for these videos.

[@AtticPhilosophy]

Glad you like them!

[@craigbareet1607]

Concise and to the point. Much appreciation from Australia.

[@AtticPhilosophy]

Thanks!

[@jay1900]

I am really struggling to apply the rules in this problem, can you please give me some guidance: Using the natural deduction rules, give a formal proof of: (A → [B → C]) ([A ∧ B] → C) from no premises.

[@AtticPhilosophy]

You have to prove left-to-right and then right-to-left. For the former, Assume the left, prove the right. To prove the right, assume the antecedent A&B, use what you’ve got to get to the consequent. Right-to-left is similar.

[@bourdieufan7433]

very helpful stuff

[@AtticPhilosophy]

Glad it was helpful!

[@justincollier1042]

Quick question: Would you need to use parentheses for (p ^ q ^ r). Either way you disambiguate it, you get the same result.

[@AtticPhilosophy]

You're right: you don't need to (because, as you say, it's the same meaning either way). Officially, p ^ q ^ r isn't a well-formed sentence, whereas ((p^q)^r) and (p^(q^r)) are. But in practise, it's fine to drop parentheses when they don't change the meaning, as in the case of p^q^r.

[@justincollier1042]

@@AtticPhilosophy Thank you!

[@dancingdoungnut]

@@AtticPhilosophy Does that mean that ((p^q)^r) (p^(q^r))?

[@AtticPhilosophy]

@@dancingdoungnut They're different but equivalent sentences - they always have the same truth-value.

[@chiyokuoni5658]

Thx it's helping me a lot!

[@AtticPhilosophy]

No problem! Glad it helped.

[@abu5197]

Is propositional logic a form of classical logic since a proposition is either true or false? Is this not similar to the Law of Excluded middle?

[@AtticPhilosophy]

Propositional logic is logic without quantifiers (words like every and some). It’s any kind of logic that uses ps and qs combined with connectives (like and, or) to form sentences. So propositional logic doesn’t have to be classical: there is intuitionistic propositional logic and paraconsistent propositional logic and relevant propositional logic, none of which are classical. But when you’re being introduced to propositional logic at an early stage of learning logic, it will 99% of the time be classical logic.

[@abu5197]

@@AtticPhilosophy Thanks for the quick clarification!

[@raunaqverma7905]

Is this for computer science? I got a book about natural deduction and searched it up and came here up untill this point i am not able to understand a thing . Should i complete this playlist? Reply will be appreciated 🙏🙏

[@AtticPhilosophy]

Yes, propositional logic & natural deduction are used & taught in theoretical computer science. You might want to skip the philosophy-focused videos.

[@raunaqverma7905]

@@AtticPhilosophy thanks I saw 4 videos and now I am starting to understand a bit. Thanks.Nice Videos btw.😇

[@Lucidthinking]

Hi Mark, Thanks for your great videos. There is something that is quite confusing to me, and I hope you can help me understand. At 8:39 you wrote the sentence: p ^ (q v r) will go to the party. From the sentence we can get two obvious possible conclusions: p and q will go to the party p and r will got to the party Can we also conclude that they all will go to the party? Because if we affirm that each of them will go to the party we will still get a true sentence. If this is the case, it seems that it is not what you wanted to convey in the sentence. It seems that you meant to use exclusive or. i.e. p ^ ( q ⊕ r )

[@AtticPhilosophy]

Yes, q v r allows both q,r to be true, so p&(q v r) allows all three to be true.

[@nou-kc1ws]

💝💝💝💝

[@billwatters4833]

Maybe it's my age but the introductory music is horrific to my old ears. It sounds like some boys in the garage banging on empty oil drums. Let's have something more conducive to quiet thinking, please. Other than that bit of mild criticism may I say that I have learned more from this site than any other channel purporting to teach philosophy.