Theorem aev2 1986

Description: A version of aev 1983 with two universal quantifiers in the consequent, and a generalization of hbaevg 1984. One can prove similar statements with arbitrary numbers of universal quantifiers in the consequent (the series begins with aeveq 1982, aev 1983, aev2 1986).

Using aev 1983 and alrimiv 1855 (as in aev2ALT 1987), one can actually prove (with no more axioms) any scheme of the form (∀𝑥𝑥 = 𝑦 → PHI) , DV (𝑥, 𝑦) where PHI involves only setvar variables and the connectors →, ↔, ∧, ∨, ⊤, =, ∀, ∃, ∃*, ∃!, Ⅎ. An example is given by aevdemo 27317. This list cannot be extended to ¬ or ⊥ since the scheme ∀𝑥𝑥 = 𝑦 is consistent with ax-mp 5, ax-gen 1722, ax-1 6-- ax-13 2246 (as the one-element universe shows).

(Contributed by BJ, 29-Mar-2021.)

Assertion

Ref	Expression
aev2	⊢ (∀𝑥 𝑥 = 𝑦 → ∀𝑧∀𝑡 𝑢 = 𝑣)

Distinct variable group:   𝑥,𝑦

Proof of Theorem aev2

Dummy variables 𝑤 𝑠 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		hbaevg 1984	. 2 ⊢ (∀𝑥 𝑥 = 𝑦 → ∀𝑧∀𝑤 𝑤 = 𝑠)
2		aev 1983	. 2 ⊢ (∀𝑤 𝑤 = 𝑠 → ∀𝑡 𝑢 = 𝑣)
3	1, 2	sylg 1750	1 ⊢ (∀𝑥 𝑥 = 𝑦 → ∀𝑧∀𝑡 𝑢 = 𝑣)

Syntax hints:   → wi 4  ∀wal 1481

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1722  ax-4 1737  ax-5 1839  ax-6 1888  ax-7 1935

This theorem depends on definitions:  df-bi 197  df-an 386  df-ex 1705

This theorem is referenced by: (None)