In the Twenty Verses, Vasubandhu offers an elaborate defense of idealism. His arguments may be summarized as follows: Because non-existing entities can be consciously apprehended, consciousness must have ontological priority (VVS I, 1). The typical realist objection to an assertion of this sort concerns the causal function of perception: indeed, if mental content can be said to consciously arise without any reference to external objects, then why does it arise at a specific time and place and no