Samkhya or Sankhya (IAST: sāṃkhya) is one of the six orthodox schools of Hindu philosophy. It is described as the rationalist school of Indian philosophy. It is most related to the Yoga school of Hinduism, and its rationalism was influential on other schools of Indian philosophies.
Sāmkhya is an enumerationist philosophy whose epistemology accepted three of six Pramanas as the only reliable means of gaining knowledge. These included Pratyakṣa (perception), Anumāṇa (inference) and Sabda (Āptavacana, word/testimony of reliable sources).
Samkhya is strongly dualist. Sāmkhya philosophy regards the universe as consisting of two realities; Puruṣa (consciousness) and prakriti (matter). Jiva (a living being) is that state in which puruṣa is bonded to prakriti in some form. This fusion, state the Samkhya scholars, led to the emergence of buddhi (“spiritual awareness”) and ahankara (individualized ego consciousness, “I-maker”). The universe is described by this school as one created by Purusa-Prakriti entities infused with various permutations and combinations of variously enumerated elements, senses, feelings, activity and mind. During the state of imbalance, one of more constituents overwhelm the others, creating a form of bondage, particularly of the mind. The end of this imbalance, bondage is called liberation, or moksha by Samkhya school of Hinduism.
The existence of God or supreme being is not directly asserted, nor considered relevant by the Samkhya philosophers. Sāṃkhya denies the final cause of Ishvara (God). While Samkhya school of Hinduism considers the Vedas as a reliable source of knowledge, it is an atheistic philosophy according to Paul Deussen and other scholars. A key difference between Samkhya and Yoga schools, state scholars, is that Yoga school of Hinduism accepts a "personal, yet essentially inactive, deity" or "personal god".
Samkhya is known for its theory of gunas (qualities, innate tendencies). Guna, it states, are of three types: Sattva being good, compassionate, illuminating, positive, and constructive; Rajas guna is one of activity, chaotic, passion, impulsive, potentially good or bad; and Tamas being the quality of darkness, ignorance, destructive, lethargic, negative. Everything, all life forms and human beings, state Samkhya scholars, have these three gunas, but in different proportions. The interplay of these gunas defines the character of someone or something, of nature and determines the progress of life. The Samkhya theory of gunas was widely discussed, developed and refined by various schools of Indian philosophies including Buddhism. Samkhya's philosophical treatises also influenced the development of various theories of Hindu ethics.