Ancient Indian philosophy includes six orthodox schools and several heterodox ones.

Classical “orthodox” (āstika) schools are often counted as six (e.g., Nyāya, Vaiśeṣika, Sāṃkhya, Yoga, Mīmāṃsā, Vedānta). “Heterodox” (nāstika) traditions include major streams like Buddhism and Jainism, plus others.