因明入正理論疏 2.145

2.145

述曰：指不定相。猶者，如也。夫立論宗，因、喻能立，舉因無喻，因何所成？其何等可舉方比？因既無方，明因不定，不能生他決定智故。

The commentary explains: This points out the nature of being inconclusive. "Like" (*yóu*) means "as" (*rú*). When a proponent establishes a proposition, the reason and example are the instruments of proof; if one cites a reason without an example, what can the reason establish? What could be cited to compare it with? Since the reason lacks a comparable case, it is evident that the reason is inconclusive, because it cannot produce determinate cognition in the opponent.