 Vasubandhu defines the perfect nature as the ultimate truth and identifies it with mere-consciousness. “This is the ultimate (paramārtha) of the dharmas, and so it is the reality (tathatā) too. Because its reality is like this all the time, it is mere consciousness.” (Triṃ 25, Sems tsam shi 3b) Accordingly Sthiramati’s Commentary on the Thirty Verses (Triṃśikābhāṣya [TriṃB], Sems tsam shi 146b–171b), explains “ultimate” (paramārtha) here as referring to “’ world-transcending knowledge’ (lokottara-nirvikalpa-jñāna) in that there is nothing that surpasses it. Since it is the object of [the transcendent knowledge], it is the ultimate. It is even like the space in having the same taste everywhere. It is the perfect nature, which is stainless and unchangable. Therefore, it is known as the ‘ultimate.’” ([TriṃB], Sems tsam shi 169ab)