大乘百法明門論開宗義決 1.106

1.106

若心心所無能緣相乃至亦是能緣等者。此立見分亦有二量。第一量云。心心所法應不能緣。宗也。無能緣相故。因也。如虛空等。喻也。第二量云。或虛空等亦是能緣。宗也無能緣相故。因也。如心心所。喻也。虛空等者。等取真如及色法等。覆合並例准而作之。

Regarding "If mind and mental factors had no subjective aspect, up to, would also be a cognizer": this establishes the subjective aspect (darśana-bhāga) also through two syllogisms. The first syllogism states: Thesis: Minds and mental factors would not be able to cognize. Reason: Because they lack a subjective aspect. Example: Like space and so forth. The second syllogism states: Thesis: Or else space and so forth would also be cognizers. Reason: Because they lack a subjective aspect. Example: Like mind and mental factors. By "space and so forth", tathatā, material dharmas, and so forth are included. The contrapositives and extensions are to be constructed analogously.