Question

Use Fitch system to proof ((p ⇒ q) ⇒ p) ⇒ p without any premise. ONLY FOR FITCH SYSTEM.

score 6.9k · Answer 1 · 2017-04-05 22:01:59

6.9k

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Use Fitch system to proof ((p ⇒ q) ⇒ p) ⇒ p without any premise. ONLY FOR FITCH SYSTEM.

Published on 05 Apr 2017 - 22:01

score 75 · Answer 2 · 2026-03-25 03:03:46

75

Views

Proof of distributivity of $\land$ over $\lor$ using disjE in natural deduction

Published on 25 Mar 2026 - 3:03

score 115 · Answer 3 · 2023-02-07 22:31:35

115

Views

Prove that contrapositive rule is equivalent to the rule of double negation

Published on 07 Feb 2023 - 22:31

score 133 · Answer 4 · 2023-02-12 19:37:24

133

Views

Trying to understand "Deriving natural deduction rules from truth tables" and having trouble with false hypothetical judgments

Published on 12 Feb 2023 - 19:37

score 79 · Answer 5 · 2023-02-13 14:22:09

79

Views

What does it mean to discard a hypotesis in a natural deduction?

Published on 13 Feb 2023 - 14:22

score 165 · Answer 6 · 2023-02-14 16:50:10

165

Views

How to prove $\neg q \rightarrow \neg p \vdash p \rightarrow q$ and $\neg (p \lor q) \vdash \neg p \land \neg q$ by natural deduction?

Published on 14 Feb 2023 - 16:50

score 84 · Answer 7 · 2023-02-15 18:25:02

84

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How to prove ¬p ∧ ¬q ⊢ ¬(p ∨ q) by natural deduction?

Published on 15 Feb 2023 - 18:25

score 98 · Answer 8 · 2026-03-25 14:34:32

98

Views

Can this rule of inference do replace axiom of extensionality?

Published on 25 Mar 2026 - 14:34

score 159 · Answer 9 · 2023-02-24 04:34:52

159

Views

How/where is this technique generalised and proven for other (standard, first order) logical operations (if possible)? A method of natural deduction.

Published on 24 Feb 2023 - 4:34

score 108 · Answer 10 · 2023-03-06 14:16:01

108

Views

Soundness and completeness of Fitch-style for first order logic

Published on 06 Mar 2023 - 14:16

score 63 · Answer 11 · 2026-02-23 06:42:05

63

Views

Proof in Natural Deduction, Sequent Calculus or Hilbert System

Published on 23 Feb 2026 - 6:42

score 132 · Answer 12 · 2023-03-23 11:57:27

132

Views

Prove that $¬(A → B) ⊢ ¬(¬A ∨ B)$ in natural deduction

Published on 23 Mar 2023 - 11:57

score 120 · Answer 13 · 2023-04-04 20:18:56

120

Views

Help with Formal Proof using introduction and elimination rules

Published on 04 Apr 2023 - 20:18

score 144 · Answer 14 · 2023-04-13 15:34:26

144

Views

Use natural deduction to prove ((¬P ∧ ¬Q) → ¬(P ∨ Q)) using primitive rules only

Published on 13 Apr 2023 - 15:34

score 165 · Answer 15 · 2026-03-22 15:43:13

165

Views

Linear logic as Fitch-style natural deduction?

Published on 22 Mar 2026 - 15:43

List Question

Use Fitch system to proof ((p ⇒ q) ⇒ p) ⇒ p without any premise. ONLY FOR FITCH SYSTEM.

Proof of distributivity of $\land$ over $\lor$ using disjE in natural deduction

Prove that contrapositive rule is equivalent to the rule of double negation

Trying to understand "Deriving natural deduction rules from truth tables" and having trouble with false hypothetical judgments

What does it mean to discard a hypotesis in a natural deduction?

How to prove $\neg q \rightarrow \neg p \vdash p \rightarrow q$ and $\neg (p \lor q) \vdash \neg p \land \neg q$ by natural deduction?

How to prove ¬p ∧ ¬q ⊢ ¬(p ∨ q) by natural deduction?

Can this rule of inference do replace axiom of extensionality?

How/where is this technique generalised and proven for other (standard, first order) logical operations (if possible)? A method of natural deduction.

Soundness and completeness of Fitch-style for first order logic

Proof in Natural Deduction, Sequent Calculus or Hilbert System

Prove that $¬(A → B) ⊢ ¬(¬A ∨ B)$ in natural deduction

Help with Formal Proof using introduction and elimination rules

Use natural deduction to prove ((¬P ∧ ¬Q) → ¬(P ∨ Q)) using primitive rules only

Linear logic as Fitch-style natural deduction?

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