Patanjali of the Yoga Sutras was probably not the famous grammarian of the same name
Tradition praises one sage Patanjali for purifying the mind with yoga, speech with grammar and the body with medicine. Most modern scholars see at least two or three different men behind those texts, and the one-author story cannot be traced before about the 10th or 11th century.
The grammarian is the easiest to pin down. His Mahabhashya, a vast commentary on the grammar of Panini and the notes of Katyayana, is dated with reasonable confidence to the middle of the 2nd century BCE. For more than 2,000 years he has counted as the last great authority on classical Sanskrit grammar, and the Chinese pilgrim I-tsing reported that advanced Indian students spent three years mastering his book.
The yoga Patanjali is much harder to date. Estimates run from the 2nd century BCE to the 5th century CE. Radhakrishnan and Moore tied the text to the grammarian and the Maurya period; Philipp Maas places it around 400 CE; Edwin Bryant notes that most scholars favour the first or second century CE. The Yoga Sutras consist of 196 aphorisms and became the foundation of classical yoga philosophy in Hinduism.
Why doubt a single author? Louis Renou found clear differences of language, grammar and vocabulary between the two texts, which never refer to each other. The idea that one sage wrote on grammar, yoga and medicine surfaces in the 11th-century commentary of King Bhoja, perhaps prompted by an unnamed polymath in a verse by Bhartrhari. Medical writings credited to a Patanjali are either lost or later still, possibly by one or two further scholars. Traditional circles and modern yoga culture nevertheless often treat the unified sage as an article of faith, and Tamil Shaiva tradition counts him among its 18 siddhars.
The yoga text's fortunes swung dramatically. In medieval times it was translated into about forty Indian languages as well as Old Javanese and Arabic, making it the most translated ancient Indian text. Then it faded for nearly 700 years, overshadowed by works such as the Bhagavad Gita, until Swami Vivekananda and others revived it in the late 19th century.
Source: Patanjali
