Nyāya Sūtras 2.22

2.22

asty ayam ity anujñāyamāno 'rthaḥ siddhāntaḥ/ sa ca prameyam/ tasya pṛthagvacanaṃ satsu siddhāntabhedeṣu vādajalpavitaṇḍāḥ pravartante, nāto 'nyatheti/

An established tenet is an object acknowledged as 'this is so'. And it is an object of valid cognition. Its separate mention is because, while different varieties of established tenets exist, philosophical debate, disputation, and cavil proceed, and not otherwise.