Order Topology is Hausdorff

Theorem
Let $\struct {X, \preceq, \tau}$ be a linearly ordered space.

Then $\struct {X, \tau}$ is a Hausdorff space.

Proof
Let $x, y \in X$ with $x \ne y$.

Since $\le$ is a total ordering, either $x \prec y$ or $y \prec x$.

, assume that $x \prec y$.

If there is a $z \in X$ such that $x \prec z \prec y$, then ${\downarrow}z$ and ${\uparrow}z$ separate $x$ and $y$.

Otherwise, by Mind the Gap, ${\downarrow}y$ and $\uparrow x$ separate $x$ and $y$.

Since any two distinct points can be separated by neighborhoods, $\left({X, \tau}\right)$ is a Hausdorff space.