in Katyayana. Metaphysics as grammatical motivation Unlike Pāṇini's objectives in the Ashtyadhyayi, which is to distinguish correct forms and meanings from incorrect ones (shabdaunushasana), Patanjali's objectives are more metaphysical. These include the correct recitations of the scriptures (Agama), maintaining the purity of texts (raksha), clarifying ambiguity (asamdeha), and also the pedagogic goal of providing an easier learning mechanism (laghu). This stronger metaphysical bent has also been indicated by some as one of the unifying themes between the Yoga Sutras and the Mahābhāṣya, although a close examination of actual Sanskrit usage by Woods showed no similarities in language or terminology. The text of the was first critically edited by the 19th-century orientalist Franz Kielhorn, who also developed philological criteria for distinguishing Kātyāyana's "voice" from Patañjali's. Subsequently, a number of other editions have come out, the 1968 text and translation by S.D. Joshi and J.H.F. Roodbergen often being considered definitive. Regrettably, the latter work is incomplete. Patanjali is often stated as having claimed there was a hostility between the orthodox Brahminic (Astika) groups and the heterodox, nAstika groups (Buddhism, Jainism, and atheists), like that between a mongoose and a snake. Nathan McGovern argues Patanjali never used this mongoose-snake analogy. Patanjali also sheds light on contemporary events, commenting on the recent Greek incursion, and also on several tribes that lived in the Northwest regions of the subcontinent. Patanjalatantra Patanjali is also the reputed author of a medical text called Patanjalah, also called Patanjala or Patanjalatantra. This text is quoted in many yoga and health-related Indian texts. Patanjali is called a medical authority in a number of Sanskrit texts such as Yogaratnakara, Yogaratnasamuccaya, Padarthavijnana, Cakradatta bhasya. Some of these quotes are unique to Patanjala, but others are also found in major Hindu medical treatises such as Charaka Samhita and Sushruta Samhita. There is a fourth scholar also named Patanjali, who likely lived in 8th-century and wrote a commentary on Charaka Samhita and this text is called Carakavarttika. The two medical scholars named Patanjali may be the same person, but generally accepted to be completely different person than the Patanjali who wrote the Sanskrit grammar classic Mahabhasya. Legacy Patanjali is honoured with invocations and shrines in some modern schools of yoga, including Iyengar Yoga and Ashtanga Vinyasa Yoga. The yoga scholar David Gordon White writes that yoga teacher training often includes "mandatory instruction" in the Yoga Sutra. White calls this "curious to say the least",