Sankhya was one of the six orthodox systems (astika, those systems that recognize vedic authority) of Hindu philosophy. Srila Prabupada has pointed out that the original theistic Sankhya philosophy was propounded by sage Kapila in the Srimad Bhagavatam long before another atheistic form of Samkhya-yoga was enunciated by an imposter Kapila. The major text of this Vedic school is the extant Samkhya Karika, written by Ishvara Krishna, circa 200 AD. There are no purely Sankhya schools existing today in Hinduism, but its influence is felt in the Yoga and Vedanta schools.
Sankhya is an enumerationist philosophy but many scholars have misunderstood it as strongly dualist. That is an inaccurate view. Sankhya philosophy regards the universe as consisting of two realities: Purusha (consciousness) and Prakriti (phenomenal realm of matter). Purusha, the cosmic consciousness, is the basis of Prakriti, its material nature. They are the experiencer and the experienced, not unlike the res cogens and res extensa of Descartes. Prakriti further bifurcates into animate and inanimate realms. On the other hand, Purusha separates out into countless Jivas or individual units of consciousness as souls which fuse into the mind and body of the animate branch of Prakriti. This was a dualistic philosophy. But there are differences between Sankhya and Western forms of dualism. In the West, the fundamental distinction is between mind and body. In Sankhya, however, it is between the self (as Purusha) and matter (Prakriti). The real Sankhya (as a theistic school of thought) can be thus seen as a type of dualist monism which is quite different from Western forms of dualism.
Sankhya cites two kinds of perceptions: Indeterminate (nirvikalpa) perceptions and determinate (savikalpa) perceptions.
Indeterminate perceptions are merely impressions without understanding or knowledge. They reveal no knowledge of the form or the name of the object. There is only external awareness about an object. There is cognition of the object, but no discriminative recognition.
For example, a baby’s initial experience is full of impression. There is a lot of data from sensory perception, but there is little or no understanding of the inputs. Hence they can be neither differentiated nor labeled. Most of them are indeterminate perceptions.
Determinate perceptions are the mature state of perceptions which have been processed and differentiated appropriately. Once the sensations have been processed, categorized, and interpreted properly, they become determinate perceptions. They can lead to identification and also generate knowledge.
Purusha is the Transcendental Self or Pure Consciousness. It is absolute, independent, free, imperceptible, unknowable, above any experience and beyond any words or explanation. It remains pure, “nonattributive consciousness ”. Purusha is neither produced nor does it produce.
Prakriti is matter. Matter is inert, temporary, and unconscious. It is composed of three qualities (trigunas) of the self. They are:
All physical events are considered to be manifestations of the evolution of Prakrti, or primal nature (from which all physical bodies are derived). Each sentient being is a Purusha, and is limitless and unrestricted by its physical body. Samsaara or bondage arises when the Purusha does not have the discriminate knowledge and so is misled as to its own identity, confusing itself with the physical body - which is actually an evolute of Prakriti. The spirit is liberated when the discriminate knowledge of the difference between conscious Purusha and unconscious Prakriti is realized.
The original school of Sankhya was founded by Sage Kapila which was a theistic philosophy and fully described in Srimad Bhagavatam. However, later on an imposter Kapila announced that there was no philosophical place for a creationist God in this system. He argued that the existence of Ishvara cannot be proved and hence cannot be admitted to exist. The imposter Kapila's school also argued that an unchanging Ishvara as the cause cannot be the source of a changing world as the effect. The fake atheistic Sankhya system did not garner much support. Later on, the original theistic Sankhya system was revived which included Ishvara. There is a common misunderstanding that the concept of Ishvara was incorporated into the Sankhya viewpoint only after it became associated with the theistic Yoga system of philosophy. This can be verified by studying the original theistic Sankhya philosophy described in Srimad Bhagavatam.
More specifically, Sankhya system follows the Prakriti-Parinama Vada. Parinama denotes that the effect is a real transformation of the cause. The cause under consideration here is Prakriti or more precisely Mula-Prakriti (Primordial Matter). The Sankhya system is therefore an exponent of an evolutionary theory of matter beginning with primordial matter. In evolution, Prakriti is transformed and differentiated into multiplicity of objects. Evolution is followed by dissolution. In dissolution the physical existence, all the worldly objects mingle back into Prakriti, which now remains as the undifferentiated, primordial substance. This is how the cycles of evolution and dissolution follow each other. Sankhya theorizes that Prakriti is the source of the world of becoming. It is pure potentiality that evolves itself successively into twenty four tattvas or principles. The evolution itself is possible because Prakriti is always in a state of tension among its constituent strands -
All macrocosmic and microcosmic creation uses these templates. The twenty four principles that evolve are -
The evolution of primal nature is also considered to be purposeful - Prakrti evolves for the spirit in bondage. The spirit who is always free is only a witness to the evolution, even though due to the absence of discriminate knowledge, he misidentifies himself with it.
The evolution obeys causality relationships, with primal Nature itself being the material cause of all physical creation. The cause and effect theory of Sankhya is called Satkaarya-vaada (theory of existent causes), and holds that nothing can really be created from or destroyed into nothingness - all evolution is simply the transformation of primal Nature from one form to another.
The evolution of matter occurs when the relative strengths of the attributes change. The evolution ceases when the spirit realizes that it is distinct from primal Nature and thus cannot evolve. This destroys the purpose of evolution, thus stopping Prakrti from evolving for Purusha.
Sankhyan cosmology describes how life emerges in the universe; the relationship between Purusha and Prakriti is crucial to Patanjali's yoga system. The evolution of forms at the basis of Sankhya is quite remarkable. The strands of Sankhyan thought can be traced back to the Vedic speculation of creation. It is also frequently mentioned in the Mahabharata and Yogavasishta.
The original Sankhya philosophy of Kapila states that by devotion and service one attains the clarity of mind to have this discrimination with the grace of God. Views of what happens to the soul after liberation vary tremendously, as the Sankhya view is used by many different Hindu sects and is rarely practiced alone.