Let $P = (\Omega, \mathcal{F}, \mathbb{P})$ be a D1159: Probability space such that

(i)	$E, F_1, \ldots, F_N \in \mathcal{F}$ are each an D1716: Event in $P$
(ii)	$F_1, \ldots, F_N$ is a D5143: Set partition of $\Omega$

Then \begin{equation} \mathbb{P}(E) = \sum_{n = 1}^N \mathbb{P}(E \cap F_n) \end{equation}