大乘法苑義林章 1.49

1.49

第四何識為觀者，大眾部等說：六識有染，皆能離染。犢子部等說：五識非染亦非離染，第六俱有。薩婆多等，六識有染，離染唯第六。於大乘中，古德或說七識修道、八識修道。皆非正義，不可依據。若能觀識，因唯第六。《瑜伽》第一云「能離欲是第六意識，不共業故，通真俗、三智，餘不能起行，總緣觀理趣入真故。」《瑜伽》又云「審慮所緣唯意識故，第七由他引亦為此觀，通中、後智。佛果通八識，能為唯識觀，三智通真俗、理事二門。成事非真，唯觀俗識。」此解依論，理或有真，但真如識定非能觀。若論所觀，八識皆通因果二位，真識亦爾。

Fourth, which consciousness constitutes contemplation: The Mahāsāṃghika and others teach that all six consciousnesses are defiled and all can attain detachment from defilement. The Vātsīputrīya and others teach that the five [sense] consciousnesses are neither defiled nor free from defilement, whereas the sixth has both. The Sarvāstivādins and others hold that the six consciousnesses are defiled, but detachment from defilement belongs exclusively to the sixth. Within the Mahāyāna, ancient masters sometimes said that the seven consciousnesses cultivate the path, or that the eight consciousnesses cultivate the path. None of these is the correct doctrine, and they cannot be relied upon.
As for the contemplating consciousness, in the causal stage it is exclusively the sixth. Yogācārabhūmi, fascicle 1, states: 'That which can attain detachment from desire is the sixth mental consciousness, because of its unique function; it applies to both ultimate and conventional and to the three wisdoms; the rest cannot initiate practice, since [only the sixth] comprehensively apprehends and contemplates the principle to enter into truth.' The Yogācārabhūmi also states: 'Because deliberate investigation of the focal object belongs exclusively to mental consciousness; the seventh, induced by others, also engages in this contemplation, applying to the middle and subsequent wisdoms. In the Buddha-fruition, all eight consciousnesses are able to practice the contemplation of consciousness-only; the three wisdoms apply to both ultimate and conventional, and to both principle and phenomena. The accomplishment of actions is not ultimate, but contemplates only conventional consciousness.' This explanation relies on the treatises, and in principle there may be truth to it; however, the tathatā consciousness is definitely not the contemplating [consciousness]. If one speaks of what is contemplated, all eight consciousnesses apply to both causal and fruition stages, and the true consciousness is likewise so.