Vaisesika Sūtra 3.2.01

ātma-indriya-artha-saṁnikarṣe jñānasya bhāvaḥ-abhāvaś-ca manasaḥ liṅgam ॥1॥

The presence or lack of knowledge arising from the coming together of ātma, senses, and objects is the indication of mind (manas).