 The Converse Future Barcan Formula scheme, \(\mathsf{CBF}_{G}\), is CD-valid:  \(\models_{\mathrm{CD}} G \forall x \varphi(x) \to \forall x G \varphi(x)\) or, equivalently,   \(\models_{\mathrm{CD}} \exists x F \varphi(x) \to F \exists x \varphi(x)\).