Nyāya Sūtras 74.4

74.4

asya tu vibhāgaḥ/ pūrvaṃ hi pratiṣedhasiddhāv asati pratiṣedhye kim anena pratiṣidhyate paścāt siddhau pratiṣedhyāsiddhiḥ pratiṣedhābhāvād iti/ yugapatsiddhau pratiṣedhyasiddhyabhyanujñānād anarthakaḥ pratiṣedha iti/

The differentiation of this [is as follows]: If the denial is established beforehand, then in the absence of that which is to be denied, what is denied by this? If it is established afterward, there is no establishment of that which is to be denied, because the denial is absent. If they are established simultaneously, the denial is pointless, because the establishment of that which is to be denied is admitted.