唯識二十論述記 1.90

1.90

述曰：下廣四難，於中有二：初牒大乘義，別為四難，後總為四難。初中亦二：初牒大乘義；後正申難。此廣初句頌，通下四難。「若」者，若其事，謂若大乘說唯有識，無心外境，即是離於心外實有色、聲等境，有緣色等，能緣識生。此識生時，不以離心色等為境者。此即小乘、外道牒大乘義。

The Commentary says: Below, the four objections are treated extensively, within which there are two parts: first, quoting the Mahāyāna thesis, he separately makes four objections; second, he makes the four objections jointly. The first also has two parts: first, quoting the Mahāyāna thesis; second, properly setting forth the objections. This extensively explains the first line of the verse and applies to the four objections below. 'If' refers to if such were the case—that is, if Mahāyāna says there is vijñapti-mātra alone without objects external to the mind, this means that, apart from the mind, real objects such as forms and sounds exist, and there are cognizing consciousnesses arising that take forms and so forth as objects; and when these consciousnesses arise, they would not take forms and so forth external to the mind as their objects. This is the Hīnayāna and non-Buddhist schools quoting the Mahāyāna thesis.