Speakpigeon
Contributor
- Joined
- Feb 4, 2009
- Messages
- 6,317
- Location
- Paris, France, EU
- Basic Beliefs
- Rationality (i.e. facts + logic), Scepticism (not just about God but also everything beyond my subjective experience)
Can you think of any logical expression (formula) which are usually regarded as true but that you intuitively see as false?
I put here a few common expressions usually regarded as true:
1. ¬¬A → A
2. (A ∧ B) → B
3. A → (A ∨ B)
4. (A ∧ B) → (A ∨ B)
5. ((A ∧ (A → B)) → B
6. ((¬B ∧ (A → B)) → ¬A
7. ((A → B) ∧ (B → C)) → (A → C)
8. ((A → B) ∧ (B → C) ∧ (C → D)) → (A → D)
9. ((B → A) ∧ (C → A)) ∧ (B ∨ C)) → A
10. ((A → B) → ¬(A ∧ ¬B)) ∧ (¬(A ∧ ¬B) → (A → B))
These are pretty uncontroversial... So, please specify first whether you agree with each being true.
And then maybe you have your own examples?
EB
I put here a few common expressions usually regarded as true:
1. ¬¬A → A
2. (A ∧ B) → B
3. A → (A ∨ B)
4. (A ∧ B) → (A ∨ B)
5. ((A ∧ (A → B)) → B
6. ((¬B ∧ (A → B)) → ¬A
7. ((A → B) ∧ (B → C)) → (A → C)
8. ((A → B) ∧ (B → C) ∧ (C → D)) → (A → D)
9. ((B → A) ∧ (C → A)) ∧ (B ∨ C)) → A
10. ((A → B) → ¬(A ∧ ¬B)) ∧ (¬(A ∧ ¬B) → (A → B))
These are pretty uncontroversial... So, please specify first whether you agree with each being true.
And then maybe you have your own examples?
EB