According to current interpretations of Parmenides, he either embraces a token-monism of things, or a type-monism of the nature of each kind of thing, or a generous monism, accepting a token-monism of things of a specific type, necessary being. These interpretations share a common flaw: they fail to secure commensurability between Parmenides’ alētheia and doxa. We effect this by arguing that Parmenides champions a metaphysically refined form of material monism, a type-monism of things; that light and night are allomorphs of what-is (to eon); and that the key features of what-is are entailed by the theory of material monism.