Higher Homotopy Groups are Abelian

Theorem
Let $X$ be a topological space.

Let $x_0\in X$.

Let $n\geq2$ be a integer.

Let $\pi_n(X, x_0)$ be the $n$th homotopy group with base point $x_0$.

Then $\pi_n(X, x_0)$ is abelian.