金剛經纂要刊定記 6.163

6.163

而以等者，以前文云是名具足色身，是名諸相具足，彼中意者，法身畢竟非相好，相好亦非不佛，由無相故現，相不離法身，所以疑云：既無相故方能現相，則但見於相，便知無相也。如遠見煙定知有火，以離於火必無煙故。

"Yet by means of..." and so forth: because the earlier text said "is called the complete physical body" and "is called the completeness of all marks". The intent therein is that the dharmakāya is ultimately not the marks and signs, yet the marks and signs are not non-Buddha; because it is markless, it manifests, and the marks are not separate from the dharmakāya. Therefore the doubt is: since it is only because it is markless that it can manifest marks, then merely by seeing marks, one would know the markless. It is like seeing smoke in the distance and definitively knowing there is fire, because apart from fire there is certainly no smoke.