Indian philosophy comprises the philosophical traditions of the Indian subcontinent. Since medieval India (ca.1000–1500), schools of Indian philosophical thought have been classified by the Brahmanical tradition as either orthodox or non-orthodox – āstika or nāstika – depending on whether they regard the Vedas as an infallible source of knowledge. There are six schools of orthodox Hindu philosophy—Nyaya, Vaisheshika, Samkhya, Yoga, Mīmāṃsā and Vedanta—and three heterodox schools—Jain, Buddhist and Cārvāka. However, there are other methods of classification; Vidyaranya for instance identifies sixteen schools of Indian philosophy by including those that belong to the Śaiva and Raseśvara traditions.