rūpasyāpyālokarahitasya kaiścit prāṇiviśeṣair upalambhāt tasmād vipakṣe bhāvāsambhavānnānaikāntiko hetuḥ
Because color without light is perceived by certain special beings [i.e. animals], therefore, since [the reason's] presence in the counter-instance is impossible, the reason is not inconclusive