 For Vasubandhu, everything that is real or substantial (dravya) is causally efficient, having specifiable cause-and-effect relations with other entities. Everything that does not have such a causal basis is unreal, and if anything, it is merely a conceptual construct, a mere convention (prajñapti). The so-called “person,” like everything else, must be one or the other—real or unreal, causally conditioned or conceptually constructed. Vasubandhu places it in the latter category. Notice that, to call something a “conceptual construction” (parikalpita) is, for Vasubandhu, to remove it from the flow of causality. Abstract entities have no causal impetus and are unreal. This is Vasubandhu’s formalization, and expansion, of the Buddhist doctrine that all conditioned things are impermanent. Some Buddhists accept (for instance) that space and nirvana are real, though unconditioned. Vasubandhu says, instead, that all things that are engaged with the causal world must be, themselves, conditioned (this is a corollary of his proof of momentariness), so he rejects the causal capacity of eternal, unchanging entities. But even setting aside Vasubandhu’s expanded view, it is clearly out of the question for Buddhists to say that the self is unconditioned and eternal. That is a non-Buddhist view, which Vasubandhu treats later on.