One of these is the unique interpretation of emptiness and dependent origination found in the Madhyamaka school. Another very influential doctrine for Mahāyāna is the main philosophical view of the Yogācāra school variously, termed "Vijñaptimātratā-vāda" ("the doctrine that there are only ideas" or "mental impressions") or "Vijñānavāda" ("the doctrine of consciousness"). According to Mark Siderits, what classical Yogācāra thinkers like Vasubandhu had in mind is that we are only ever aware of mental images or impressions, which may appear as external objects, but "there is actually no such thing outside the mind." There are several interpretations of this main theory, many scholars see it as a type of Idealism, others as a kind of phenomenology.