Vasubandhu, an advocate of the idealist Yogācāra school of Buddhism, argues that the nonexistence of external objects can be inferred from the appearance of nonexistent things in perceptual illusion. The idealist view and the argument from illusion are criticized by proponents of the realist Nyāya school on the grounds that illusory experience is parasitic upon veridical experience. The parasitism objection successfully defeats Vasubandhu's argument from illusion but fails to decisively disprove the idealist view because it remains possible that each illusory experience gets its content from a previous illusory experience in an infinite chain.