Ultrafilter.exists_le

∀ {α : Type u} (f : Filter α) [h : f.NeBot], ∃ u, ↑u ≤ f

The ultrafilter lemma: Any proper filter is contained in an ultrafilter.

Defined in: Mathlib.Order.Filter.Ultrafilter.Defs
Cited by: 2 results in Mathlib
Foundations: Depth 73 from the axioms · uses propext, Classical.choice, Quot.sound
Assumes: Filter.NeBot

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