 Other operators that can be considered hybrid temporal logic operators are the universal modality, the difference modality, and propositional quantifiers. The universal modality \(A\) says that a given formula is true at every instant of the temporal modal and hence captures the global notion of truth in a model: \(\mathcal{M},t\vDash A\varphi\) iff \(\mathcal{M}\vDash\varphi\). The difference modality \(D\), on the other hand, states that the given formula is true at some other instant. Note that both modalities abstract away from the underlying accessibility relation. Propositional quantifiers \(\forall p\) introduce second-order quantification into the propositional language, and we discuss them in  Section 7.3  below.