成唯識論述記 9.166

9.166

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.