# Kelley's Theorem

## Theorem

Let $\struct {D, \preceq}$ be a directed set,

Let $S$ be a non-empty set.

Let $n: D \to S$ be a net in $S$.

Then $n$ has a universal subnet.

## Axiom of Choice

This theorem depends on the Axiom of Choice.

Because of some of its bewilderingly paradoxical implications, the Axiom of Choice is considered in some mathematical circles to be controversial.

Most mathematicians are convinced of its truth and insist that it should nowadays be generally accepted.

However, others consider its implications so counter-intuitive and nonsensical that they adopt the philosophical position that it cannot be true.

## Source of Name

This entry was named for John Leroy Kelley.