俱舍論記 28.41

28.41

「若許於彼至此有何理」者，又縱許牒破。若許於彼無色界中有色根身，破云：如何可言彼色微少？若謂於彼身量小故名無色者，破云：水細虫極微，亦應名無色，小不可見故。若謂身極清妙故名無色者，破云：中有、色界應名無色，亦清妙故。若謂彼身清妙中極故名無色，中有、色界清妙非極不名無色，破云：應唯有頂得無色名，清妙中極故，如定有勝劣、上下不同，生身亦有勝劣、上下不等，故有頂最勝。若言彼色非下地眼見故名無色，破云：又生四靜慮所有色身，非下地眼所能取故，與彼無色何異，不名無色？此即以下同上。若謂欲、色隨義立名，實有欲、色名欲、色界。無色不然，非隨義立，雖實有色而名無色。此有何理？

As for "If one admits that in that realm... what reason is there for this?": this is further citing their thesis under a concession and refuting it. If you admit that there is a physical sense-organ body in that formless realm, the refutation says: How could one say that its form is subtle and scarce? If you say it is called formless because the body's size is small, the refutation says: Minute insects in water and subtle atoms should also be called formless, because they are small and cannot be seen. If you say it is called formless because the body is extremely fine and pure, the refutation says: The intermediate existence (antarābhava) and the form realm should be called formless, because they are also fine and pure. If you say that that body is called formless because it is the utmost in being fine and pure, whereas the intermediate existence and the form realm are not called formless because their fine purity is not the utmost, the refutation says: Then only the summit of existence (bhavāgra) should obtain the name formless because its fine purity is the utmost; just as concentrations have distinctions of superior and inferior, higher and lower, the bodies of rebirth also have inequalities of superior and inferior, higher and lower, so the summit of existence is the most superior. If you say that it is called formless because that form cannot be seen by the eyes of lower stages, the refutation says: Furthermore, since the physical bodies of all those born in the four dhyānas cannot be grasped by the eyes of lower stages, how are they different from that formless realm such that they are not called formless? This equates the lower with the upper. If you say that the desire realm and the form realm are named according to their actual meaning—real desire and real form exist, so they are called the desire realm and the form realm—whereas the formless realm is not so, not being named according to its actual meaning, so that although form really exists it is called formless: what reason is there for this?