In this paper. I argue that the modality contained in declarative sentences is heterogeneolls by nature. and its indiscernible treatment evoked pardoxical behaviors of individuals in modal contexts. The diflkult~r is avoided by cla5sifying the modality in two kinds from a normative point of vin\``: 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 tl``eated in the traditional modal logic. but the latter kind of modality which typically appears in belief sentences is captured in another framework called multi톗odel. This solution deeply concerns the ontology of individuals. therefore the existential presupposition of individuals. too. So. I further propose its treatment hy llleans of a kind of three-valued semantics.