Nyāya Sūtras 2.27

2.27

tadāśrayā ca tattvavyavasthā/ te caite 'vayavāḥ śabdaviśeṣāḥ santaḥ prameye 'ntarbhūtā evamarthaṃ pṛthag ucyanta iti/
tarko na pramāṇasaṃgṛhīto, na pramāṇāntaram, pramāṇānām anugrāhakas tattvajñānāya kalpate/ tasyodāharaṇam --- kim idaṃ janma kṛtakena hetunā nirvartyate, āhosvid akṛtakena, athākasmikam iti?

And on it rests the settlement of reality. And these components, being specific types of words, are included within the object of valid cognition; they are mentioned separately for this purpose.
Hypothetical reasoning is not included among the means of valid cognition, nor is it another means of valid cognition; aiding the means of valid cognition, it serves for the knowledge of reality. Its example is: 'Is this birth produced by a produced cause, or by an unproduced one, or is it uncaused?'