Theorem mopickr 39001

Description: "At most one" picks a variable value, eliminating an existential quantifier. The proof begins with references *2.21 (pm2.21 124) and *14.26 (eupickbi 2664) from [WhiteheadRussell] p. 104 and p. 183. (Contributed by Peter Mazsa, 18-Nov-2024.) (Proof modification is discouraged.)

Assertion

Ref	Expression
mopickr	⊢ ((∃*𝑥𝜓 ∧ ∃𝑥(𝜑 ∧ 𝜓)) → (𝜓 → 𝜑))

Proof of Theorem mopickr

Step	Hyp	Ref	Expression
1		exancom 1891	. . 3 ⊢ (∃𝑥(𝜑 ∧ 𝜓) ↔ ∃𝑥(𝜓 ∧ 𝜑))
2		moeu2 39000	. . . 4 ⊢ (∃*𝑥𝜓 ↔ (¬ ∃𝑥𝜓 ∨ ∃!𝑥𝜓))
3		19.8a 2217	. . . . . . . 8 ⊢ (𝜓 → ∃𝑥𝜓)
4	3	con3i 155	. . . . . . 7 ⊢ (¬ ∃𝑥𝜓 → ¬ 𝜓)
5		pm2.21 124	. . . . . . 7 ⊢ (¬ 𝜓 → (𝜓 → 𝜑))
6	4, 5	syl 18	. . . . . 6 ⊢ (¬ ∃𝑥𝜓 → (𝜓 → 𝜑))
7	6	a1d 26	. . . . 5 ⊢ (¬ ∃𝑥𝜓 → (∃𝑥(𝜓 ∧ 𝜑) → (𝜓 → 𝜑)))
8		eupickbi 2664	. . . . . 6 ⊢ (∃!𝑥𝜓 → (∃𝑥(𝜓 ∧ 𝜑) ↔ ∀𝑥(𝜓 → 𝜑)))
9		sp 2219	. . . . . 6 ⊢ (∀𝑥(𝜓 → 𝜑) → (𝜓 → 𝜑))
10	8, 9	biimtrdi 256	. . . . 5 ⊢ (∃!𝑥𝜓 → (∃𝑥(𝜓 ∧ 𝜑) → (𝜓 → 𝜑)))
11	7, 10	jaoi 870	. . . 4 ⊢ ((¬ ∃𝑥𝜓 ∨ ∃!𝑥𝜓) → (∃𝑥(𝜓 ∧ 𝜑) → (𝜓 → 𝜑)))
12	2, 11	sylbi 220	. . 3 ⊢ (∃*𝑥𝜓 → (∃𝑥(𝜓 ∧ 𝜑) → (𝜓 → 𝜑)))
13	1, 12	biimtrid 245	. 2 ⊢ (∃*𝑥𝜓 → (∃𝑥(𝜑 ∧ 𝜓) → (𝜓 → 𝜑)))
14	13	imp 411	1 ⊢ ((∃*𝑥𝜓 ∧ ∃𝑥(𝜑 ∧ 𝜓)) → (𝜓 → 𝜑))

Syntax hints:  ¬ wn 3   → wi 4   ∧ wa 400   ∨ wo 860  ∀wal 1568  ∃wex 1809  ∃*wmo 2565  ∃!weu 2596

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1825  ax-4 1839  ax-5 1940  ax-6 1997  ax-7 2038  ax-10 2176  ax-11 2192  ax-12 2213

This theorem depends on definitions:  df-bi 210  df-an 401  df-or 861  df-tru 1573  df-ex 1810  df-nf 1814  df-mo 2567  df-eu 2597

This theorem is referenced by: (None)