The Two-Kind and the Three-Kind Ontology in Plato’s Timaeus

At the beginning of his cosmological speech (27d–28a) Timaeus sets forth a distinction between two kinds of entities: those that are eternal and intelligible and those that are generated and are the object of opinion and sense-perception. In section 1 I examine the ontological side of this distinction, arguing that it amounts to a distinction between forms and sensible particulars and showing that forms, in contrast with sensible particulars, are presented as the only real (i.e. fully-fledged or fundamental) entities. In section 2 I examine the epistemological side of the distinction, trying to understand what the relation between opinion and sense-perception is and why sense-perception is described by Timaeus as alogos, lacking a reasonable account. This leads me to discuss some related material, i.e. Timaeus’ famous claim that his own account of the origin of the cosmos will be a ‘likely account’ (29bd) and an argument which Timaeus advances later on (51be) to establish the distinction between forms and sensible particulars and which shares some features with his initial distinction. In section 3 I turn to the part of the dialogue (48b–52d) where Timaeus introduces a ‘third kind’, the ‘receptacle of all coming-to-be’. I provide a detailed analysis of his controversial argument and defend several views: that the Receptacle is the only entity in the sensible world provided with a stable essential nature; that Timaeus adopts a very strong notion of essence, stronger than the one used by Plato’s Socrates in the Phaedo and by Aristotle; that the essential nature of the Receptacle is to be an amorphous spatial substratum and, as such, a constituent of sensible particulars; that sensible particulars are conceived of as regions of the Receptacle characterized by forms. I discuss whether or not Timaeus countenances particular instance-forms and come to the conclusion that he might be doing so, although strictly speaking it would be possible to interpret the text without having recourse to that hypothesis.