pramāṇaṣaṭkavijñāto yatrārtho nānyathā bhavan adṛṣṭaṃ kalpayatyanyaṃ sārthāpattir udāhṭtā
When a fact known through the six means of cognition, being otherwise inexplicable, leads to the assumption of another unseen [fact], that is called Arthāpatti [Presumption].