大乘義章 1.71

1.71

問曰：向說正因起法名曰因生，緣因起法說為緣生。因緣既殊，何不分二，乃合為一？釋言：別立，理亦無傷。但以此二別體起法，其義相似，故合為一。又如向說因生緣生，亦有其義，故為一矣。

Question: Earlier it was said that direct causes giving rise to dharmas is called 'arising from causes', while conditioning causes giving rise to dharmas is said to be 'arising from conditions'. Since causes and conditions are different, why not divide them into two, rather than combining them into one? Answer: Setting them up separately is logically harmless as well. However, because both give rise to dharmas with distinct substances and their meanings are similar, they are combined into one. Furthermore, as explained earlier, 'arising from causes' and 'arising from conditions' also possess these meanings; hence they constitute one.