Vaisesika Sūtra 3.2.18

अहमिति मुख्ययोग्याभ्यां शब्दवत् व्यतिरेकाव्यभिचाराद् विशेषसिद्धेर्नागमिकः ॥१८॥

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

[अहम् (aham) - I; इति (iti) - thus; मुख्ययोग्याभ्यां (mukhya-yogyābhyāṁ) - by primary and suitable usage; शब्दवत् (śabdavat) - like a word; व्यतिरेक (vyatireka) - exclusion; अव्यभिचारात् (avyabhicārāt) - due to non-deviation; विशेषसिद्धेः (viśeṣa-siddheḥ) - established due to distinct speciality; न (na) - not; आगामिकः (āgāmikaḥ) - inferable;]

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