Let $M = (\Omega, \mathcal{F})$ be a D1108: Measurable space.
Let $\mathbb{P} : \mathcal{F} \to [0, \infty]$ be a D198: Probability measure on $M$.

Then \begin{equation} \mathbb{P}(\mathcal{F}) \subseteq [0, 1] \end{equation}