Nyāya Sūtras 2.28

2.28

evam avijñāte 'rthe kāraṇopapattyā ūhaḥ pravarttate --- yadi kṛtakena hetunā nirvartyate, hetūcchedād upapanno 'yaṃ janmocchedaḥ/ athākṛtakena hetunā, tato hetūcchedasyāśakyatvād anupapanno janmocchedaḥ/ athākasmikam, ato 'kasmān nirvartyamānaṃ na punar nivartsyatīti nivṛttikāraṇaṃ nopapadyate, tena janmānuccheda iti/ etasmiṃs tarkaviṣaye karmanimittaṃ janmeti pramāṇāni pravarttamānāni tarkeṇānugṛhante,

When an object is thus unknown, conjectural reasoning proceeds through the plausibility of causes: 'If it is produced by a produced cause, then this cessation of birth is plausible through the destruction of the cause. If, on the other hand, it is by an unproduced cause, then, because the destruction of the cause is impossible, the cessation of birth is implausible. If it is uncaused, then that which is produced without a cause will not cease again, so a cause of cessation is implausible; therefore there would be no cessation of birth.' When this is the object of hypothetical reasoning, the means of valid cognition operating [to prove] that birth is caused by karma are aided by hypothetical reasoning;