成唯識論述記 9.166

9.166

述曰：結上文也。由此道理二性不一、異，諸法與法性理必應然。依他是法，如是法性，道理應爾。所以者何？勝義、世俗相待立故。謂若有俗，理必有真；若無真時，待何為俗？非龜毛望兔角可說異、一，以體無故。若有真時，理必有俗；若無俗者，待何為真？由斯道理故，前三真亦名為俗，真家俗故，故後三俗，亦名為真，俗家真故。如斯勝理，故彼二性非異、非一。

The Commentary states: This concludes the preceding text. By this reasoning, the two natures are neither one nor different; dharmas and dharmatā must necessarily be so in principle. The other-dependent is a dharma, and tathatā is dharmatā; in principle it ought to be so. Why is this? Because ultimate truth and conventional truth are established in mutual dependence. That is to say, if conventional truth exists, in principle there must be ultimate truth; if there were no ultimate truth, in dependence on what would there be conventional truth? One cannot speak of difference or oneness between turtle hair and rabbit horns, because they lack substance. If there is ultimate truth, in principle there must be conventional truth; if there were no conventional truth, in dependence on what would there be ultimate truth? By this principle, the first three ultimate truths are also called conventional truths, because they are conventional from the perspective of ultimate truth; and the latter three conventional truths are also called ultimate truths, because they are ultimate from the perspective of conventional truth. Through such supreme reasoning, those two natures are therefore neither different nor one.