成唯識論述記 6.261

6.261

述曰：下難古說有四：一、體無別難；二、不相應難；三、非實有難；四、不遍善難。此初二難也。執彼羞恥為此二別相，應此二體無有差別，相無異故。既爾，二體定不相應，無二受、二想等體有此俱起義故，二量可知。

The Commentary states: The objections below to ancient expositions have four parts: first, the objection that their substances have no difference; second, the objection that they would not be associated; third, the objection that they are not real existents; fourth, the objection that they would not pervade wholesome [minds]. These are the first two objections. If one holds that feeling shame is the distinct characteristic of these two, their two substances should have no difference, because their characteristics are not distinct. Since that is so, the two substances definitely could not be associated, because there is never such a principle where two substances of sensation, two perceptions, or the like arise together; the two formal inferences (pramāṇa) can be known.