成唯識論述記 2.292

2.292

述曰：若爾，即應唯與事業及欲同為同分，不與眼等色、聲、觸等相似法，為其同分。若許事、欲外亦與為因，但內相似皆有因者，即應外法色等相似應類亦有同分。量云：汝外相似色處法上應有同分；色處攝故；如內色處。如此徵逐亦順其理。又以理說，無始宿習為因，於今事業起同事、欲，何要別執有實同分？

The Commentary states: If so, then it should only be the commonality for common activities and desires, and not serve as the commonality for similar dharmas such as the eye, form, sound, and touch. If you admit that it also serves as a cause for things other than activities and desires, and that all internal similar [dharmas] have a cause, then external dharmas such as similar form and the like should analogously also have commonality. The inference is: Your external dharmas included in the form āyatana should possess commonality; because of being included in the form āyatana; just like the internal form āyatana. Pursuing [the argument] like this also accords with reason. Furthermore, speaking according to reason, beginningless past habitual tendencies serve as the cause for giving rise to common activities and desires at present; why must one separately grasp at the existence of a real commonality?