CABool not cartesian closed

Question

I was reading a proof I missed in class that the category $CABool$ (of complete atomic Boolean algebras) is not cartesian closed by showing first that $CABool$ is equivalent to the category $Set^{op}$. While this is a very nice idea, is it obvious why the latter is not cartesian closed?

Answer 1

$\mathbf{Set}^\mathrm{op}$ is not cartesian closed, because $1 + X \not\cong 1$ in general. (In a cartesian closed category, $0 \times X \cong 0$.)