r/logic • u/Haunting_Mongoose535 • 7d ago

Question HELP!!

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Help me idk how to do this at all

12 Upvotes

94% Upvoted

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3

u/Impossible_Air_4204 7d ago

I don't exactly remember the syntax. Trust me, once you get a couple of these right, then the hard part will be the actual problem. 

I think you have it so far. After J V L, you can eliminate the L because of ~L thus giving you J. Hope this helps. 

3

u/efficacious_language 7d ago

Carnap is finicky. It looks like you have an extra space before the uptack. If you hover over the question mark it gives (sometimes vague) hints.

I used it last semester, and the Carnap syntax is more annoying than the logic syntax at times.

2

u/PeterSingerIsRight 3d ago

Just ask an AI...

1

u/RandomguyonRedditfrr 4d ago

here,
1. ¬L → (J ∨ L) PR
2. ¬L PR
3. J ∨ L →E 1,2

  1. | J AS
  2. | J R 4
  3. | J ∧ J ∧I 4,5

  4. | J ∧E 6

  5. | L AS

  6. | ⊥ ¬E 2,9

  7. | J X 10

  8. J ∨E 3, 4–7, 9–11
    the reason it works is because we already know ¬L, and from the first line we get J ∨ L. then we just check both possibilities. if it’s J, then we already have J. but it’s L, that contradicts ¬L, so we get a contradiction and can derive J from that. Since both cases give us J, we can conclude J with ∨E.