From Sanskrit sam, "union; completeness," and khya, "to be known; knowledge" — i.e., to have complete knowledge; to attain the ultimate wisdom, or Self-realization and God-union
Sankhya is dualistic. It regards the universe as consisting of two realities,
purusha (consciousness) and
Jiva (a living being) is that state in which puruṣa is bonded to prakṛti in some form.
One of the six principal systems of Hindu philosophy, Sankhya expounds the why of religion, Vedanta describes the end to be attained, and Yoga provides the method for that attainment. Together, these concepts constitute true religion, whose twofold purpose is to show man how to avoid suffering and how to contact the bliss of the Supreme One: that lasting happiness which is not conditioned by either painful or pleasant experiences. Thus religion has two phases.
Sankhya philosophy has to do with the first phase, pointing out that the primary goal of everyone is the avoidance of spiritual, mental, and physical suffering. However, we can live in a painless state and still not be happy. There are a lot of people who are suffering, and a few who are not, but it doesn't necessarily follow that those who are for the moment unafflicted are happy. The state of painlessness is agreeable, but is not itself happiness-producing. To attain true and lasting happiness, which Vedanta describes as the end or second phase of religion, a full understanding and application of the principles of religion are necessary. This is Yoga.
There are two beginningless realities: prakriti and purusha, the female and the male principle, matter and spirit. Ideally, before the development of concrete existences, they exist separately in polarity. In actual existence they are combined and interacting. Purusha, in himself pure consciousness, experiences the changes that prakrti, on account of her three gunas, is undergoing, as if these were his own. Purushas are originally many; prakrti is originally one. The association with a purusa makes prakrti, as the evolved being, manifold and makes purusa interact with it. Under the influence of purusa, out of the unevolved primordial prakrti, develop macrocosm and microcosm according to a fixed pattern. Each part of it is characterized in a different measure by the presence of the three gunas. Originally the three gunas—sattva or lightness, rajas or passion, and tamas or darkness—had been in equilibrium in prakrti. Under purusa's influence the equilibrium is disturbed and evolution begins. (K. Klostermaier)
The Gita I:39:
The ultimate wisdom of Sankhya I have explained to thee. But now thou must hear about the wisdom of Yoga, equipped with which, O Partha (Arjuna), thou shalt shatter the bonds of karma.
According to Sankhya, the twenty-four principles of the evolutionary process of Nature, from Spirit into matter, are as follows:
(1) Prakriti (the basic creative power bringing forth all phenomena);
(2) Mahat-tattva (Cosmic Intelligence; referred to in Yoga as chitta) from which comes buddhi (individual discriminative intelligence);
(3) ahamkara (egoism);
(4) manas (mind);
(5-14) jnanendriyas and karmendriyas (ten senses—five of perception and five of action);
(15-19) tanmatras (five supersensible or abstract qualities of matter);
(20-24) mahabhutas (five subtle elements or vibratory motions, the conglomeration of which appear as gross matter in solid, liquid, fiery, gaseous, and etheric form).