Consciousness-only is the foundation of a buddhist theory known as vijnanavada. Proponents, notably the Yogacara school, suggest that the sum of experience exists only in our minds. Philosophers recognition of this view as subjective idealism is a matter of discussion because these traditions often deny the existence of ontological subject. These views are rooted in the denial of existence of any kind of ontological substance (as Matter, Soul, God, etc.). Consciousness-only views can also be found in taoist philosophy, notably Lao Tzu and Chuang Tzu.