In Indian philosophy, idealism has been a common view in both Buddhist and Hindu traditions. In his Twenty Verses, an in-depth defense of idealism, the 4th-century-CE Yogācāra philosopher Vasubandhu starts by attributing idealism to the Buddha: Everything in the three realms is nothing but mind. Or as Vasubandhu puts it: Reality is consciousness only. On Vasubandhu’s view, when I see a tree, all there is in reality is the idea of a tree, or the appearance of a tree, or consciousness of a tree. There is no tree outside the mind.
