成唯識論演祕 6.163

6.163

釋曰：此經部難，若言有心定有心法，如何滅定唯有心王？經部滅定唯有心故。論是彼宗過，我大乘宗若處有心，必定亦有心相應法；若處無有心，相應法心亦定無，如是三界皆唯有心，此言顯示三界唯識。言三界者，謂與欲等愛結相應墮在三界。

Explanation: This is an objection by the Sautrāntika: "If you say that where there is citta there must be caitasikas, why in the attainment of cessation is there only the mind-king?" For according to the Sautrāntika, the cessation attainment has only citta. The treatise shows the fault in their school: in our Mahāyāna school, wherever there is citta, there must also be associated caitasikas; wherever there are no caitasikas, citta also definitely does not exist. Thus the three realms are all cittamātra; this statement reveals that the three realms are vijñapti-mātra. The phrase "the three realms" refers to being associated with the fetters of craving of desire and so forth, falling within the three realms.