The Bud of Nyāya 1.20

1.20

dharmaḥ kṛtakatvamiṣyate tarhi samānadharmayogāt tayoraviśeṣe tadvadeva
sarvapadārthināmaviśeṣaḥ prasajyata iti | upapattyā pratyavasthānamupapattisamā jātirbhavati | yadi kṛtakatvopapattyā śabdasyānityatvaṃ
tadā niravayavatvopapattyā nityatvamapi kasmānna bhavatīti
pakṣadvayopapattyā'nadhyavasāyaparyavasādhanatvaṃ vivakṣitamityudbhāvanaprakārabheda evāyam | upalabdhyā pratyavasthānamupalabdhisamā
jātirbhavati | anityaḥ śabdaḥ prayatnanantarīyaktvāditi prayukte paraḥ pratyavatiṣṭhate ? na khalu prayatnanantarīyaktvamanityasādhanam | sādhanaṃ hi taducyate yena vinā na sādhyamupalabhyate | upalabhyate ca prayatnanānantarīyaktvena vinā'pi vidyudādāvanityatvam | śabde'pi kvacidvāyuvegavibhajyamānavanaspatyādijanye'pi ca
anupalabdhyā pratyavasthānamanupalabdhisamā jātirbhavati | tatraiva
prayatnanānantarīyaktve hetāvyanyaste paraḥ pratyavatiṣṭhate | na
prayatnakāryaḥ śabdaḥ prāguccāraṇādastyeva āvaraṇayogāttu nopalabhyate | āvaraṇānupalambhe'pyanupalambhānnāstyeva śabda iti
cenna, āvaraṇātupalavdheranupalambhāt | āvaraṇānupalabdheśca
anupalambhādabhāvaḥ | tadabhāve cāvaraṇopalabdherbhāvo bhavati
tataśca mṛdantaritamūlakīlodakādivadāvaraṇopalabdhikṛtameva śabdasya prāguccāraṇādagrahaṇamiti | prayatnakāryatvābhāvānnityaḥ
śabda iti | sādhyadharmanityatvavikalpena śabdanityatvāpādanaṃ
nityasamā jātirbhavati | anityaḥ śabda iti pratijñāte jātivādī
vikalpayati-yeyamanityatā śabdasya ucyate sā kiṃ nityā'nityā veti | yadyanityā tadiyamavaśyamapāyinī | anityatāyā