Theorem merco1 1715

Description: A single axiom for propositional calculus discovered by C. A. Meredith.

This axiom is worthy of note, due to it having only 19 symbols, not counting parentheses. The more well-known meredith 1643 has 21 symbols, sans parentheses.

See merco2 1738 for another axiom of equal length. (Contributed by Anthony Hart, 13-Aug-2011.) (Proof modification is discouraged.) (New usage is discouraged.)

Assertion

Ref	Expression
merco1	⊢ (((((𝜑 → 𝜓) → (𝜒 → ⊥)) → 𝜃) → 𝜏) → ((𝜏 → 𝜑) → (𝜒 → 𝜑)))

Proof of Theorem merco1

Step	Hyp	Ref	Expression
1		ax-1 6	. . . . . 6 ⊢ (¬ 𝜒 → (¬ 𝜃 → ¬ 𝜒))
2		falim 1558	. . . . . 6 ⊢ (⊥ → (¬ 𝜃 → ¬ 𝜒))
3	1, 2	ja 186	. . . . 5 ⊢ ((𝜒 → ⊥) → (¬ 𝜃 → ¬ 𝜒))
4	3	imim2i 16	. . . 4 ⊢ (((𝜑 → 𝜓) → (𝜒 → ⊥)) → ((𝜑 → 𝜓) → (¬ 𝜃 → ¬ 𝜒)))
5	4	imim1i 63	. . 3 ⊢ ((((𝜑 → 𝜓) → (¬ 𝜃 → ¬ 𝜒)) → 𝜃) → (((𝜑 → 𝜓) → (𝜒 → ⊥)) → 𝜃))
6	5	imim1i 63	. 2 ⊢ (((((𝜑 → 𝜓) → (𝜒 → ⊥)) → 𝜃) → 𝜏) → ((((𝜑 → 𝜓) → (¬ 𝜃 → ¬ 𝜒)) → 𝜃) → 𝜏))
7		meredith 1643	. 2 ⊢ (((((𝜑 → 𝜓) → (¬ 𝜃 → ¬ 𝜒)) → 𝜃) → 𝜏) → ((𝜏 → 𝜑) → (𝜒 → 𝜑)))
8	6, 7	syl 17	1 ⊢ (((((𝜑 → 𝜓) → (𝜒 → ⊥)) → 𝜃) → 𝜏) → ((𝜏 → 𝜑) → (𝜒 → 𝜑)))

Syntax hints:  ¬ wn 3   → wi 4  ⊥wfal 1553

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8

This theorem depends on definitions:  df-bi 206  df-tru 1544  df-fal 1554

This theorem is referenced by:  merco1lem1  1716  retbwax2  1718  merco1lem2  1719  merco1lem4  1721  merco1lem5  1722  merco1lem6  1723  merco1lem7  1724  merco1lem10  1728  merco1lem11  1729  merco1lem12  1730  merco1lem13  1731  merco1lem14  1732  merco1lem16  1734  merco1lem17  1735  merco1lem18  1736  retbwax1  1737