For any statement $\varphi$, we define
\[[\varphi] = \begin{cases} 1, & \text{if $\varphi$ is true}; \\ 0, & \text{if $\varphi$ is false}. \end{cases}\]
For any statement $\varphi$, we define
\[[\varphi] = \begin{cases} 1, & \text{if $\varphi$ is true}; \\ 0, & \text{if $\varphi$ is false}. \end{cases}\]