Vaisesika Sūtra 8.2.02

द्रुष्टेषु भावादद्रुष्टेश्वभावात् ॥२॥

druṣṭeṣu bhāvād adruṣṭeṣv abhāvāt ॥2॥

[द्रुष्टेषु (druṣṭeṣu) - in the seen ones; भावात् (bhāvāt) - because of becoming; अद्रुष्टेषु (adruṣṭeṣu) - in the unseen ones; अभावात् (abhāvāt) - because of non becoming;]

Because of becoming in the observed ones, and because of not becoming in the unobserved ones.