成唯識論演祕 7.383

7.383

有義：今說三心為非安立者，對十六心。若對一心，無相見道亦名安立，二空真如四勝義中屬第三故。

One opinion states: Stating here that the three minds are 'non-conventional' is in contrast to the sixteen minds. If contrasted with the single-mind [real見道], the signless path of vision is also called conventional, because the twofold-emptiness true suchness belongs to the third among the four kinds of ultimate truth.