Vaisesika Sūtra 3.2.18

aham iti mukhya-yogyābhyāṁ śabdavat vyatireka-avyabhicārāt viśeṣa-siddheḥ na āgāmikaḥ ॥18॥

Since "I" by primary and suitable usage does not deviate and is established due to its distinct speciality, and is not inferable.