Indian thinkers distinguish between literal and non-literal meaning early in their history. They do so within different intellectual disciplines (śāstra-s), each broadly philosophical, but with varying emphases. Within the grammatical discipline, Yāska’s Semantic Explanation (Nirukta), an early (perhaps 6th century to 3rd century BCE) etymological treatise recognizes the difference between ordinary (laukika) and metaphorical language (upamā). This text, possibly pre-dating the renowned Sanskrit grammarian Pāṇini (ca 4th century BCE), employs etymological analysis in order to ascertain the meanings of unfamiliar terms used in the Vedas, a collection of texts including religious hymns, poetry, and rituals. In portions of the Vedas called Upaniṣads, widely recognized as proto-philosophical, the limits of language are made explicit: ordinary speech cannot characterize ultimate reality, though figurative language can hint at it. These early texts focus on topics which would give rise to three intellectual disciplines: Grammar, Philosophy, and Aesthetics. (Capital letters distinguish the schools of thought from their subject matter.)