Kant’s Ontology of Appearances and the Synthetic Apriori

Abstract Kant’s ontology of appearances implies that the numerical distinctness of empirical objects is grounded in their appearance-aspect, more precisely in space as pure intuition, in which alone such objects can be given. With distinguishing concepts things can only be thought: in contrast to Leibniz’s complete concepts and to Kripke’s rigid designators, Kant’s general concepts do not entail their referents analytically. They must be applied to intuition, i. e. be completed synthetically. Consequently, Kant’s ontology of merely singular (but not unique) individuals (Einzeldinge) is closely connected with a genuine semantics of synthetic reference via intuition, expressed by irreducible demonstratives such as “this”, “here”, and “now”. Accordingly, the judgment “There can be (or could have been) indiscernibles” is synthetic-apriori, which distinguishes Kant’s view both from skeptical empiricism and from heavyweight ontological realism.