Theorem aeveq 2085

Description: The antecedent ∀𝑥𝑥 = 𝑦 with a disjoint variable condition (typical of a one-object universe) forces equality of everything. (Contributed by Wolf Lammen, 19-Mar-2021.)

Assertion

Ref	Expression
aeveq	⊢ (∀𝑥 𝑥 = 𝑦 → 𝑧 = 𝑡)

Distinct variable group:   𝑥,𝑦

Proof of Theorem aeveq

Dummy variable 𝑢 is distinct from all other variables.

Step	Hyp	Ref	Expression
1		aevlem 2084	. 2 ⊢ (∀𝑥 𝑥 = 𝑦 → ∀𝑢 𝑢 = 𝑧)
2		ax6ev 1996	. . 3 ⊢ ∃𝑢 𝑢 = 𝑡
3		ax7 2043	. . . 4 ⊢ (𝑢 = 𝑧 → (𝑢 = 𝑡 → 𝑧 = 𝑡))
4	3	aleximi 1859	. . 3 ⊢ (∀𝑢 𝑢 = 𝑧 → (∃𝑢 𝑢 = 𝑡 → ∃𝑢 𝑧 = 𝑡))
5	2, 4	mpi 21	. 2 ⊢ (∀𝑢 𝑢 = 𝑧 → ∃𝑢 𝑧 = 𝑡)
6		ax5e 1939	. 2 ⊢ (∃𝑢 𝑧 = 𝑡 → 𝑧 = 𝑡)
7	1, 5, 6	3syl 19	1 ⊢ (∀𝑥 𝑥 = 𝑦 → 𝑧 = 𝑡)

Syntax hints:   → wi 4  ∀wal 1565  ∃wex 1806

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1822  ax-4 1836  ax-5 1937  ax-6 1994  ax-7 2035

This theorem depends on definitions:  df-bi 210  df-an 401  df-ex 1807

This theorem is referenced by:  aev  2086  2ax6e  2509  aevdemo  30751  wl-moteq  38056  wl-spae  38063