Individuals and Modality

In this paper, I argue that the modality contained in declarative sentences is heterogeneous by nature, and its indiscernible treatment evoked pardoxical behaviors of individuals in modal contexts. The difficulty is avoided by classifying the modality in two kinds from a normative point of view: 1) modality in a traditinal sense, which is a freedom under a certain convention, and 2) multi-modality which stems from the difference of conventions. The former is treated in the traditional modal logic, but the latter kind of modality which typically appears in belief sentences is captured in another framework called multi-model. This solution deeply concerns the ontology of individuals, therefore the existential presupposition of individuals, too. So, I further propose its treatment by means of a kind of three-valued semantics.