Samkhya or Sankhya (, IAST: ) is one of the six āstika (orthodox) schools of Indian philosophy. It is most related to the Yoga school of Hinduism, and it was influential on other schools of Indian philosophy. Sāmkhya is an enumerationist philosophy whose epistemology accepts three of six pramanas (proofs) as the only reliable means of gaining knowledge. These include pratyakṣa (perception), anumāṇa (inference) and śabda (āptavacana, word/testimony of reliable sources). Sometimes described as one of the rationalist school of Indian philosophy, this ancient school's reliance on reason was neither exclusive nor strong.