成唯識論了義燈 4.77

4.77

「然彼所依，總有三種」者。問：心、心所法，起藉四緣，何故但說三種依耶？解云：所緣通內外，餘三唯在內，故但說三。問：餘識緣內外，不得說四依。第七唯內緣，何不說四依？答：三緣生識勝故，但說三依，緣依亦外緣，力微不說四。問：境界生心劣，故不說四依，所緣引識微，應非二和起。　答：二和通遠近，根、境並為緣，依義據親近，境疏不說依。又云：不例，三緣依聲中說，所緣緣者是於聲說，此明所依，故彼非例。

Regarding 'However, its bases are of three kinds in total': Question: The mind and mental factors arise by relying on the four conditions (pratyaya); why are only three kinds of bases mentioned? Explanation: The objective condition (ālambanapratyaya) extends to both internal and external, while the other three are solely internal; hence only three are stated. Question: The other consciousnesses cognize internal and external objects and cannot be said to have four bases; the seventh cognizes solely the internal, so why does it not speak of four bases? Answer: Because the three conditions are pre-eminent in generating consciousness, only three bases are stated; the objective condition basis also involves external objects, and its power is weak, so four are not stated. Question: If the external object is inferior in generating the mind and therefore four bases are not spoken of, then since the objective condition induces consciousness weakly, it should not arise from the harmony of the two [sense-faculty and object]. Answer: The harmony of the two extends to both the distant and the near: faculty and object are both conditions. The meaning of 'basis' is based on intimate closeness; the object is distant, so it is not called a basis. Another explanation says: it is not a parallel case; the three conditions are spoken of in the locative case (locative of support), whereas the objective condition is spoken of in the accusative case; here we clarify the basis (āśraya), so that is not parallel.