 Two early texts which discuss inference (anumāna), but not argument (sādhana), are Ṣaṣṭi-tantra (Sixty doctrines), attributed Vārṣagaṇya (4th century ce), and Vaiśeṣika-sūtra (Aphorisms on individuation), a treatise of speculative ontology attributed to Kaṇāda (c. 1st century ce).