大般涅槃經疏 28.21

28.21

「我於一時」下，第十一爭論有三無為無三無為。然諸部中不見計無三無為者，何有此文？此亦有意，若成論人云：三無為既同是無為，寧有異體？此即是計無三無為。數人計三無為別有異體，既言三種，豈無異體？此即計有三無為義。

From "At one time, I" below, this is the eleventh debate, on whether there are three unconditioned dharmas or no three unconditioned dharmas. However, among the various schools one does not see any that posit that there are no three unconditioned dharmas; why then is there this text? This also has a meaning: if according to the followers of the *Tattvasiddhi-śāstra*, since the three unconditioned dharmas are equally unconditioned, how could they have different essences? This is precisely positing that there are no three unconditioned dharmas. The Sarvāstivādins posit that the three unconditioned dharmas have distinct essences; since one speaks of three kinds, how could they lack different essences? This is precisely the position that there are three unconditioned dharmas.