Rule of Assumption/Boolean Interpretation

Definition
Let $\mathbf A$ be a propositional formula.

The truth value of $\mathbf A$ under a boolean interpretation $v$ is given by:


 * $v \left({\mathbf A}\right) = \begin{cases}

T & : v \left({\mathbf A}\right) = T \\ F & : v \left({\mathbf A}\right) = F \end{cases}$