Sankhya is one of the earliest philosophical schools of thought in India, traditionally attributed to Rishi Kapila. His original work Shastritantra is unfortunately lost. The earliest source of this school we have today is Sankhya Karika of Isvara Krishna with the commentary known as Tattva Kaumudi by a great erudite scholar Vacaspati Mishra . Sankhya Sutras with a commentary known as Vritti by Aniruddha and another commentary known as Sankhya Pravacana Bhashya by Vijnanabhikshu are the other extant texts.Sankhya is one of the atheist philosophies. It differs from other schools mainly in its attribution of “reality” to dual entities – Purusha and Prakriti. It projects the world to be an interplay between the two everlasting Purusha and Prakriti. PRAKRITI: Prakriti is said to be the cause for the manifest universe at both physical and psychological levels. It forms the most basic constituent of matter. Matter here includes both our physical and psychological worlds. But prakriti itself has no cause. Prakriti is a state of equilibrium of the three Gunas: Sattva, Rajas and Tamas. Prakriti is also a generic term for these three gunas. Sattva denotes lightness or freedom, rajas restlessness and tamas heaviness. These may be found in different proportions in various objects of the world. A substance is classified as satva or rajas or tamas depending on its dominant property. For long philosophers have made an attempt to find the simple elements out of which complex matter is formed, the simple elements being those which cannot be reduced further to any simpler parts. Some like the Naiyaikas end their search with the atoms while the Sankhya ends with “feelings.” Feelings denote the most subtle and simple elements of nature. The Three Gunas are thus not qualities but certain feeling substances. Prof S.N. Dasgupta says in the History of Indian Philosophy, Vol I, that as per Sankhya, thought and matter are but two modifications of certain subtle substances which are in essence but three types of feeling entities. Matter gives rise to certain sensations which we equate with feelings about certain objects. Feelings later develop into certain knowledge about that particular object. However, if we go deeper than this, we would notice that even when the sensations disappear what is left is just the crude feeling out of which both thoughts and sensations evolve. Without the prior existence of feelings, there would be neither thoughts nor any external stimulus. Both of these can be reduced to mere feelings. Consequently feelings may be said to have an objective existence. This position does not make Sankhya a type of idealism like the one advocated by Berkeley. Berkley says that objects do not exist apart from our ideas of them. Objects may exist apart from our subjective feelings about corresponding external objects. However for Sankhya psychological notions and the external objects are in essence not different from feelings which have a wider existence than both the subject and the object of knowledge. There are broadly three types of feelings: pleasure, pain and dullness which are the manifestations of the three types of feeling substances called: sattva, rajas and tamas (gunas) respectively. These are regarded as the ultimate substances. Sankhya divides causes into two broad categories: efficient and material. Material cause is that cause which subsists in the effect. The efficient cause is every other type of enabling cause. For example, clay is the material cause of the pot; the potter and his stick are the efficient causes. Sankhya Karika adduces five proofs to establish this theory: 1. What is non-existent cannot be brought into existence 2. Effects comprise material cause 3. All effects are not producible from all causes 4. An efficient cause can produce only that for which it is efficient and 5. The effect has the same essence as the cause. The cause has the effect existing within it in a potential form awaiting an operation to make it manifest. A non-existent entity neither can be produced nor can any causal operation be brought about on it. For example we do not get curd out of clay or cloth out of milk, because the effect has to be existent in the cause. Every entity has an essence and existence. We say an entity exists when we see that it is capable of being an object of successful activity. When we cognize a tree and go and touch it we realize that our initial cognition of tree was true and the tree actually exists. Such an entity exists in a particular space and time. But the essence of the tree or what the tree actually is, is not an object of successful activity. The essence of an object is what it really is. When we say that the effect exists in a potential form within the cause we mean to say that it has an essence that awaits a causal operation that would confer an existence on it. The cause and the effect share a common essence but a different existence. Clay and the jar are identical because they have identical essences but not an identical existence because they share different spatial and temporal properties. Existence is limited by space and time but essence knows no such limitation. This is however not to say that there is an absolute cleavage between essence and existence, for the distinction is relative to certain aspects of the entity that we wish to address. EVOLUTION OF PRAKRITI: All changes as per Sankhya are changes of the qualities only. A substance, say, clay remains the same even when transformed into a jug or any other shape. The clay and the jug are the same but conventionally we make a distinction between them based on their practical utility. A lump of clay does not have the capacity to carry water but a jug has. Thus clay and jug are essentially the same but notionally different. Again when a lump of clay is transformed into a jug we can say that clay has the power or capacity to transform itself into a jug. The substance clay is the power-holder (saktiman) and its sakti or potency is to transform into another object, a jug in this case. The substance clay and the potency are the same thing. Their distinction is merely relative but not actual, for in ordinary experience we never find these two things separately. Similarly the emanations of Prakriti are both substantive entities and forces, two aspects of one and the same thing. In all its modifications Prakriti is the same but still generates relatively new substances, the change being a change in the relative qualities but not in the essence. Thus for Sankhya the material world has five forms: a) as appearance in diverse physical characteristic qualities or attributes b) as things or substances forming the unity of genus and species or whole or unity of parts c) as subtle causes or tanmatras d) as the ultimates or universals of the three gunas, and e) in the teleological aspect as conducive to experience and salvation of souls. The gunas , if thrown off balance, try to regroup themselves in one form then another and so on in order to restore the equilibrium. When the equilibrium is restored, it is called pralaya. An evolute is produced from some of the reals of the first stage. The deficiency of the first stage which had gone forth to form new aggregate as the second stage is made good by refilling from Prakriti. By a succession of refillings, the process of evolution proceeds till we come to a stage when no new substance can evolve. The first evolute of Prakriti is mahat. This is the state in which sattva predominates. It holds within itself the buddhi of all Purushas which were lost in the Prakriti during the pralaya. The very first work of Prakriti is thus manifested by separating out of the old buddhis or minds which hold within themselves specific avidya inherent in them with reference to each Purusha. This state of evolution consisting of all collected buddhis is called buddhitattva. Looked at from this point of view it is the widest and universal existence comprising all creation and it is thus called mahat (the great one). Mahat is then disturbed by three parallel tendencies of a preponderance of sattva, rajas and tamas called ahamkaras. The ego or ahamkara is the specific expression of general consciousness which claims experience as “mine.” The function of ego is therefore called abhimanna (self-assertion). As and when the idea of the subject evolves, simultaneously the notion of an object emerges. In self-consciousness we assert our existence as opposed to the object and hence in thought subject and object are inseparable. Both appear simultaneously. The sattvik ahamkara produces manas or mind which is translucent and gives rise to the specific notion of egohood. From tamasika ahamkara through the help of rajas are generated the tanmatras, the immediately preceding causes of gross elements. These tanmatras are sabda tanmatra (the sound potential), Vayu tanmatra (touch potential), rupa tanmatra (colour potential), rasa tanmatra (taste potential) and gandha tanmatra (smell potential). The sound potential with accretion of rudiment matter from tamasika generates akasha or ether. Through the co-mingling of the atoms, the gross elements are produced.