Questions tagged [fitch]
Frederic Brenton Fitch (1908 – 1987) was an American logician who taught at Yale. He invented the Fitch-style for natural deduction. He is also famous for the paradox of knowability. The tag may also refer to natural deduction proof environments in Fitch-style calculus for giving and checking proofs.
15
questions with no upvoted or accepted answers
1
vote
0
answers
50
views
Assume: (C∧D)∨(¬C∧D); Prove: C↔D
Is it possible to prove this formally in fitch?
I found that when C is false and D is true the conclusion is false while the premise is true.
- 11
1
vote
2
answers
240
views
fitch proof. P v Q, Q→ ¬ R, ¬ P, ¬ R → ¬ S GOAL: ¬ S
Need help exercise using the FITCH program format. I'm stuck on where to start. The following 4 steps must be used to prove the goal.
P v Q
Q→ ¬ R
¬ P
¬ R → ¬ S
GOAL: ¬ S
Now I know: ¬ P and P v Q ...
- 19
1
vote
0
answers
56
views
How did Fitch's opposition to the Russell-Whitehead theory of types turn out since the 1950's?
In a footnote to Appendix C of Frederic Fitch's Symbolic Logic (page 217), Fitch writes about his article, "Self-Reference in Philosophy":
It is reprinted here in order to indicate more fully my ...
- 19.2k
0
votes
0
answers
43
views
Is the included derivation feasible? If so, would my proof be correct?
The simple derivation seems correct and intuitive, and yet I feel as if something is off.
I would greatly appreciate it if someone could double-check the provided formal proof.
Thank you in advance ...
- 63
0
votes
0
answers
119
views
fitch arrow proof
using the FITCH program and the FITCH derivation rules you should make a proof or derivation of C7 from P5 through P11.
P5: ∀x∀y(StrongPref(x,y)→ ¬StrongPref(y,x))
P6: ∀x∀y∀z((StrongPref(x,y)∧...
- 1
-1
votes
0
answers
33
views
Formal Proof with Quantifiers
∀x ((Cube(x) ∧ Large(x)) ∨ (Tet(x) ∧ Small(x)))
∀x (Tet(x) → BackOf(x, c))
∀x ¬(Small(x) ∧ Large(x))
goal: ∀x (Small(x) → BackOf(x, c))
How would one prove ∀x (Small(x) → BackOf(x, c)) in a formal ...
- 1
-1
votes
1
answer
105
views
Fitch proofs help?
I'm new to logic and can see how to write these out informally, but need some help seeing how they should be translated into formal proofs in Fitch.
- 1
-1
votes
1
answer
104
views
Help with Fitch formal proof?
I'm having trouble solving this formal proof in Fitch. I've put together most of it, but I think I need to use disjunction elim(?) at some point and am having trouble doing that.
- 1
-1
votes
2
answers
469
views
How to prove A<—>not A
So basically there are no premises, but the file I have received to start this problem has a contradiction symbol as step one. I’m not sure if this was a mistake or purposeful, and if it was ...
- 1
-1
votes
1
answer
221
views
Use the Fitch system to prove the tautology (p ∨ ¬p). Stalled for days (NOT duplicated)
First of all, please don't close this question cause I don't get the explanation given in: Use the Fitch system to prove the tautology (p ∨ ¬p)
I have been trying to solve this exercise for days ...
- 1
-1
votes
3
answers
106
views
How to prove H → M ￢H → ￢M prove H↔M?
I'm using the program Fitch and I need to make a formal proof for this:
H → M
￢H → ￢M
Prove: H↔M
Any ideas on how to do so?
- 7
-1
votes
1
answer
871
views
Language, Proof, and Logic 14.11 Fitch Proof
Been stuck on this question for awhile now and I just don't know how to get Cube(x) so that I can use ^ intro with Cube(x) and ∀y (Cube(y) → y = a) and then use ∃ intro to get the conclusion. This is ...
- 15
-1
votes
4
answers
577
views
Language Proof & Logic 8.31 Fitch Proof
Been working on this one question for the past hours and I can't ever seem to get the last step working. Any help would be appreciated!
- 15
-2
votes
1
answer
598
views
Language, Proof and Logic Exercise 14.13 (Fitch)
Having trouble proving this. I know how to prove the first conjunct of the conclusion, but not the second one. Picture shown is the attempt proof of the second conjunct (rules haven't been added yet). ...
-5
votes
2
answers
165
views
how to prove ‘¬∃xP(x)→(P(a)→Q(a))’ from no premises? fitch
I am totally lost on how to do this... can anyone help?
What does it mean? I tried to understand what it means before proof but am totally clueless
