According to Tibetan sources, this school was in protracted dialectic with the Madhyamaka tradition. However, there is disagreement among contemporary Western and traditional Buddhist scholars about the degree to which they were opposed, if at all. The main difference deals with issues of existence and the nature of emptiness. While Madhyamaka works state that asserting the existence or non-existence of anything was inappropriate (including emptiness), Yogācāra treatises often assert that the dependent nature ("paratantra-svabhāva") really exists and that emptiness is an "actual absence" that also exists. For example, the "Madhyāntavibhāga" clearly asserts that "the imagination of the nonexistent ["abhūta-parikalpa"] exists. In it duality does not exist. Emptiness, however, exists in it." Classical Yogācāra thinkers like Asaṅga and Vasubandhu critiqued Madhyamikas who "adhere to non-existence" ("nāstikas, vaināśkas") because they saw them as straying into nihilism ("ucchedavāda"). They held that there was really something which could be said to "exist", that is, "vijñapti," and that was what is described as being "empty" their system.