 By the fifth century bce, rational inquiry into a wide range of topics was under way, including agriculture, architecture, astronomy, grammar, law, logic, mathematics, medicine, phonology and statecraft. Aside from the world’s earliest extant grammar, Pāṇini’s Aṣṭādhyāyī, however, no works devoted to these topics actually date from this preclassical period. Nonetheless, scholars agree that incipient versions of the first extant texts on these topics were being formulated and early versions of them were redacted by the beginning of the common era. They include such texts as Kṛṣi-śāstra (Treatise on agriculture), Śilpa-śāstra (Treatise on architecture), Jyotiṣa-śāstra (Treatise on astronomy), Dharma-śāstra (Treatise on law), Caraka-saṃhitā (Caraka’s collection), a treatise on medicine, and Artha-śāstra (Treatise on wealth), a treatise on politics.