Commentary on the Nyāyasūtra 1.p6

Nyāyabhāṣya (complete text) 1.p6

satyupalabhyamāne tadvadanupalabdheḥ pradīpavat| yathā darśakena pradīpena dṛśye guhyamāṇe tadiva yanna gṛhyate tatrāsti|