Philosophy Now Forum

Any help is appreciated.. here is what im dealing with

I am writing everything as it appears on the worksheet

1.~XvY
2.~F
3. D (horseshoe) X
4.~Y&F
/~D&F

1.K (horseshoe) C
2. K&G
3. C (horseshoe) ~F
4. ~D
5. ~F (horseshoe) D
/~Kv~R

By (horseshoe) do you mean set union U?

If so I'm surprised to find this in predicate logic. Could you give a bit of context to where these proofs are coming from?

Arising_uk wrote:By (horseshoe) do you mean set union U?

When people say "horseshoe" they usually mean horseshoe but you can't take anything for granted round here.

I was wondering if it was just the Logic teacher showing that any symbol can be used to express some kind of logical operator or relation.

Mr. Ed used horseshoe logic...

-Imp

This is sentential logic.

Some suggestion:
1.~XvY
2.~F
3. D (horseshoe) X
4.~Y&F
-----------------------
5. ~Y conj. elim. 4.
6. F conj. elim. 4.
7. ~XvY reiteration 1.
8. | ~X
---------
9. | ~X

10. | Y
------------
11. | ~X

12. ~X disj. elim. 7.-11.
13. ~D modus tollens 3., 12.
------------------------
/~D&F conj introd. 6., 13.

Here is your "horseshoe": ⊃ from http://lukasfolsneslea.tripod.com/HTML-LN-charsym1.html.

The logic book your looking for is The Logic Book 5th ed. or so by M. Bergmann, J. Moor and J. Nelson.

Oh! Now I get it, the material conditional, doh!

He could have said 'right horseshoe' or 'left horseshoe' for a better clue.