Sankhya philosophy, considered by some to be the oldest of all the philosophical schools, was systematized by an ancient thinker named Kapila (different from the Devahuti-putra Kapila of the Srimad-Bhagavatam whose sankhya system does not exclude God). The first work of nontheistic sankhya, the Sankhya-sutra, is traditionally attributed to Kapila, but in its present form it is not his original work. So the Sankhya-karika of Isvarakrishna is actually the earliest available sankhya text. Among its more well-known commentaries are Gaudapada's bhasya, Vacaspati Misra's Tattva-kaumudi, Vijnanabhiksu's Sankhya-pravacanbhasya, and Mathara's Matharavrtti. Topics traditionally emphasized by Kapila, Isvarakrishna, and other sankhya commentators are the theory of causation, the concept of prakrti (the unconscious principle) and purusa (the conscious principle), the evolution of the world, the concept of liberation, and the theory of knowledge. The special feature of sankhya is its summing up of all of the nyaya and vaisesika constituents of reality -- with the exception of isvara, God, Who is simply excluded from the system -- into two fundamental principles: purusa and prakrti. Nirisvara sankhya (nontheistic sankhya) is therefore a dualistic philosophy.
 

The Sankhya Theory of Cause and Effect
All Indian philosophies base their explanation of the evolution or manifestation of the universe on two fundamental views of cause and effect: satkaryavada and asatkaryavada. According to satkaryavada, the effect exists in its cause prior to its production or manifestation, but the asatkaryavada position maintains that the effect does not exist in its cause prior to manifestation. This latter theory is also called arambhavada, which means "the doctrine of the origin of the effect." All other theories related to cause and effect are based on one or the other of these two fundamental positions. Sankhya philosophy accepts the satkaryavada view of causation. Regarding satkaryavada, there are two schools of thought: vivartavada and parinamavada. The first is accepted by Advaita vedantins, who hold that the change of a cause into an effect is merely apparent. For example, when one sees a snake in a rope, it is not true that the rope is really transformed into a snake; it simply appears to be that way. This theory serves as the basis for the Advaitist explanation of God, the universe and the individual soul. Sankhya philosophy upholds the view of parinamavada, according to which there is a real transformation of the cause into the effect, as in wood being transformed into a chair, or milk into yogurt.

Sankhya philosophy developed elaborate explanations to argue the parinamavada version of satkaryavada that a cause actually changes into its effect. These explanations are central to the whole sankhya system, which proceeds from the premise that the effect exists in its material cause even before the effect is produced. There are five basic arguments for this premise. The first, asadakaranat, states that the effect exists in its material cause before its production because no one can produce an effect from a material cause in which that effect does not exist. For example, no one can turn the color blue into the color yellow, nor can anyone produce milk from a chair, because yellow does not exist in blue and a chair does not exist in milk. The second argument is upadanagrahanat, which states that because there is an invariable relationship between cause and effect, material cause can produce only that effect with which it is causally related. Only milk can produce a yogurt because milk alone is materially related to yogurt. If an effect does not exist in any way before its production, then it is impossible for an effect to be related to its cause. Therefore, an effect must already exist in its cause before it is produced. The third argument, sarvasambhavabhavat, states that there is a fixed rule for the production or manifestation of things. A certain thing can be produced only by a certain other thing; it cannot be produced from just anything or anywhere. This impossibility proves that all the effects exist within their particular causes. The fourth argument, saktasya-sakya-karanat, states that an effect exists in its cause in an unmanifested form before it is produced. This is the case because only a potent cause can produce a desired effect, and the effect must therefore be potentially contained in the cause. The potentiality of cause cannot, however, be related to an effect if the effect does not exist in that particular cause in some form. The fifth argument, karanabhavat, states that if the effect does not exist in the cause, then that which was non-existent would be coming into existence out of nothing. This is as absurd as saying that the son of a barren woman once built an empire, or that people decorate their homes with flowers of the sky. Such statements have no logical correspondence to reality.

By means of these arguments, the sankhya philosophers established the theory of parinamvada or manifestation, according to which an effect is already existent in unmanifested form in its cause. The process of producing an effect from the cause or the process of manifestation and annihilation can be clarified with the analogy of the tortoise, which extends its limbs from its shell. The tortoise does not create its limbs; it merely brings that which was hidden into view. Sankhya philosophers hold that, similarly, no one can convert nonexistence into existence; nor can that which exists be entirely destroyed. A tortoise is not different from its limbs, which are subject to appearance or disappearance, just as golden ornaments such as rings and earrings are not different from the gold used to make them. The theory of manifestation is essential to sankhya philosophy and indeed serves as the basic foundation upon which all its other theories are constructed.
 

Prakrti -- The Unconscious Principle
The sankhya system holds that the entire world -- including the body, mind, and senses -- is dependent upon, limited by, and produced by the combination of certain effects. Various other schools of philosophy -- such as Carvaka, Buddhism, Jainism, Nyaya, and Vaisesika -- maintain that atoms of earth, water, fire, and air are the material causes of the world. but according to the sankhya system, material atoms cannot produce the subtler products of nature, such as mind, intellect, and ego. Therefore, one has to seek elsewhere for that cause from which gross objects and their subtler aspects are derived. If one examines nature, it becomes obvious that a cause is subtler than its associated effect and that a cause pervades its effect. For example, when a seed develops into a tree, whatever latent quality the seed contains will be found in the tree. The ultimate cause of the world must also be a latent principle of potential, and it must be uncaused, eternal, and all-pervading. It must be more subtle than the mind and intellect, and at the same time it must contain all the characteristics of the external objects as well as of the senses, mind, and intellect. In sankhya philosophy this ultimate cause is called prakrti. To prove its existence, sankhya offers the following five arguments. First, it is accepted that all the objects of the world are limited and dependent on something else, so there must be an unlimited and independent cause for their existence. That cause is prakrti. Second, all the objects of the world possess a common characteristic: they are capable of producing pleasure, pain, or indifference. Therefore, something must exist as the cause of the universe that possesses the characteristics of pleasure, pain, and indifference. That is prakrti. Third, all the objects of the world have a potential to produce something else or to convert themselves into something else. Therefore, their cause must also have the same potential, which implicitly contains the entire universe. That is prakrti. Fourth, in the process of evolution an effect arises from its cause, and in dissolution it is reabsorbed or dissolved into its origin. The particular objects of experience must therefore arise from a certain cause, which must in turn have arisen from a certain cause. and so on until one reaches the primal cause of the creative process itself. A similar process takes place in involution or annihilation. Here, physical elements are broken down into atoms, atoms are dissolved into gross energies, and gross energies into finer ones until all of these dissolve into the unmanifested One. That unmanifested One is called prakrti -- the primordial nature. Fifth, if one attempts to go further and imagine the cause of this ultimate cause, he will land himself in the fallacy of infinite regression. Ultimately one has to stop somewhere and identify a cause as the first cause of the universe. In sankhya philosophy that supreme root cause of the world is called prakrti.
 

The Gunas
Prakrti is not to be comprehended as merely the atomic substance of matter. Nor can it be taken as a conscious principle behind the material substance. And it is not a hypothetical construct of the mind (a creation of philosophy and nothing more). Prakrti means literally "exceptional ability;" it is the wonderful nature out of which the vast material world in all of its levels of intricate permutation takes shape. Prakrti is characterized by the three gunas of sattva, rajas, and tamas. The word guna may be translated as "a quality or attribute of prakrti," but it is important to note that the three gunas are not to be taken merely as surface aspects of material nature. They are, rather, the intrinsic nature of prakrti. The balanced combination of sattva, rajas, and tamas is prakrti, and thus they cannot be prakrti's external attributes or qualities. They are called gunas (that is, "ropes") because they are intertwined like three strands of a rope that bind the soul to the world. One can say that a rope is the name for three intertwined strands, but if one analyzes the strands separately, he does not see the rope. In a similar way, if he analyzes the gunas separately, one will not apprehend prakrti, since it is a balanced state of the three gunas.

According to sankhya philosophy, sattva, rajas, and tamas are the underlying qualities from which the universe we perceive is derived. These gunas can be inferred from the fact that all features of the material world -- external and internal, both the physical elements and the mind -- are found to possess the capability of producing pleasure, pain, or indifference. The same object may be pleasing to one person, painful to another, and of no concern to a third. The same beautiful girl is pleasing to her boyfriend, painful to another girl who is attracted to the same boy, and of no concern to many other people not involved. These qualities of the girl, appearing in relation to other people around her, arise from the gunas that underlie the manifested world. This example can help one see how the cause of all phenomena, prakrti, contains all the characteristics found in worldly objects.

Sankhya philosophy posits that the whole universe is evolved from the gunas. The state in which they are in their natural equilibrium is called prakrti, and when their balance is disturbed they are said to be in vikrti, the heterogeneous state. The three gunas are said by the nontheistic sankhya philosophers to be the ultimate cause of all creation. Sattva is weightlessness and light (laghu); rajas is motion or activity (calam); and tamas is heaviness, darkness, inertia, or concealment (guru and avarana). The gunas are formless and omnipresent when in a state of equilibrium, having completely given up their specific characteristics when thus submerged in each other. In a state of imbalance, however, rajas is said to be in the center of sattva and tamas, and this results in creation because manifestation in itself is an action. Action depends on motion, the force of activity that is the very nature of rajas, and so sattva and tamas are dependent on rajas to manifest themselves and thus produce pairs of opposites. Rajas also depends on sattva and tamas, however, because activity cannot be accomplished without the object or medium through which it becomes activated. In the state of manifestation, one guna dominates the other two, but they are never completely apart from each other or completely absent because they are continually reacting with one another. By the force of rajas, sattvic energy evolves with great speed and its unitary energy becomes divided into numerous parts. At a certain stage, however, their velocity decreases, and they start to come closer and closer together. With this contraction in sattvic energy, tamas is naturally manifested, but at the same time another push of the active force (rajas) occurs also on tamas, and within the contraction a quick expansion occurs. Thus do the gunas constantly change their predominance over one another. The predomination of sattva over tamas and of tamas over sattva is always simultaneously in process; the conversion of each of them into one another is taking place at every moment.

Sattva and tamas have the appearance of being in opposition to each other because one is light and weightless and the other is dark and heavy. But these pairs actually cooperate in the process of manifestation and dissolution as things move from subtle to gross and from gross to subtle. The expansion of power stores up energy in some relatively subtle form, from which it manifests to form a new equilibrium. These points of relative equilibrium constitute certain stages in the evolutionary process. It might at first seem that there is constant conflict among the gunas, but this is not the case. They are in perfect cooperation during the process of manifestation because it is through their constant interaction that the flow of cosmic and individual life continues. They are essentially different from but interrelated with one another. Just as the oil, wick, and flame of a lamp work together to produce light, so the different gunas cooperate to produce the objects of the world. The gunas play the same role in one's body and mind as they do in the universe as a whole. An individual's physical appearance is simply a manifestation of the gunas that has been brought about by consciousness. This intention of consciousness to cause prakrti to manifest disturbs the state of equilibrium in prakrti, thus causing the gunas to interact and manifest the universe.

The gunas are always changing or transforming into one another. This occurs in two ways: virupaparinama, "change into a heterogeneous state," and svarupaparinama, "change into a homogeneous state." Svarupaparinama, the first kind of transformation, takes place when one of the gunas dominates the other two and begins the process of manifestation of a particular objects. This type of transformation or interaction of the gun as with each other is responsible for the manifestation of the world. Svarupaparinama, the other kind of transformation of the gunas, refers to that state in which the gunas change internally without disturbing each other. In this state, the gunas cannot produce anything because they neither oppose nor cooperate with one another. This type of change occurs in the balanced state of prakrti. In describing the process of involution, sankhya states that all gross elements dissolve into subtle elements and finally they all dissolve into their origin -- sattva, rajas and tamas. Ultimately these three gunas also come to a state of perfect balance called prakrti. Then there remains no weight of tamas, no weightlessness of sattva, and no activity of rajas because the gunas no longer have a separate existence in the sense of predominance of any single attribute. This state -- prakrti -- cannot be perceived by one's ordinary perception; it can only be inferred. One can only imagine a state in which all of nature is balanced and there is no levity, no motion, no heaviness; no light, no darkness, no opposing forces; in which the imagination itself, being a product of the mind, is dissolved. Sankhya philosophers describe this state as uncaused, unmanifested, eternal, all-pervading, devoid of effect-producing actions, without a second, independent, and partless.
 

Purusa -- Consciousness
As was previously stated, sankhya is a dualistic philosophy that acknowledges two aspects of reality: the unconscious principal (prakrti) and consciousness (purusa or the self). Each body contains a self, but the self is different from the body, senses, mind, and intellect. It is a conscious spirit, at once both the subject of knowledge and the object of knowledge. It is not merely a substance with the attribute of consciousness, but it is rather pure consciousness itself -- a self-illumined, unchanging, uncaused, all-pervading, eternal reality. Whatever is produced or is subject to change, death, and decay belongs to prakrti or its evolutes, not to the self. It is ignorance to think of the self as body, senses, mind, or intellect, and it is through such ignorance that purusa confuses itself with the objects of the world. Then it becomes caught up in the ever flowing stream of changes and feels itself to be subject to pain and pleasure.

Sankhya offers five arguments to prove the existence of purusa. First, all the objects of the world are meant to be utilized by and for someone other than themselves. All things that exist serve simply as the means for the ends of other beings. (A chair is not made for the chair itself, nor is a house made for the house itself.) Therefore, there must be something quite different and distinct from such objects. Objects cannot enjoy their own existence, nor can one material object be utilized and enjoyed by another material object; therefore, there must be some other enjoyed of the objects. That enjoyed who utilizes the objects of the world is consciousness, purusa.

Second, it cannot be said that all objects are meant for prakrti because prakrti is unconscious and is the material cause of all objects. It is the balance of the gunas, of which all the objects of the world are composed. Prakrti is thus the potential or essence of all pain, pleasure, and neutral states and cannot therefore be the enjoyer of itself, just as even the greatest of men cannot sit on his own shoulders. The proprietor or utilizer of all worldly objects must consequently be a conscious being who does not possess the three gunas and who is completely different from them in both their balanced and heterogeneous states. That transcendent Reality is purusa.

Third, all the objects of the external world -- including the mind, senses, and intellect -- are in themselves unconscious. They cannot function without guidance from some intelligent principle, and they must be controlled and directed by it in order to achieve anything or realize any end. That conscious self who guides the operation of prakrti and its manifestations is purusa. Fourth, nonintelligent prakrti and all its evolutes, which are by nature pleasurable, painful, or neutral, have no meaning if they are not experienced by some intelligent force. That experience is purusa.

Fifth, every human being wants to attain liberation and be free from pain and misery, but whatever is derived from prakrti brings pain and misery. If there is nothing different from prakrti and its evolutes, then how is liberation attainable? If there were only prakrti, then the concept of liberation and the will to liberate or to be liberated, which is found in all human beings, in the sayings of sages, and in the scriptures, would be meaningless. Therefore, there must be some conscious principle that strives for liberation. That principle is the self, purusa.
 

Proof of the Existence of Many Selves
According to sankhya, there are many selves or conscious principles -- one in each living being. If there were only one self related to all bodies, then when one individual died, all individuals would simultaneously die, but this is not the case. The birth or death of one individual does not cause all other individuals to be born or to die; blindness or deafness in one man does not imply the same for all men. If there were only one self pervading all beings, then if one person were active, all the selves would be active; if one were sleeping, then all would sleep. But this does not happen, and there is therefore not one self but many selves. Secondly, human beings are different from God and from animal and vegetable life as well. But this distinction could not be true if God, human beings, animals, birds, insects, and plants all possessed the same self. Therefore there must be a plurality of selves that are eternal and intelligent. Thus it becomes clear that there are two realities: prakrti, the one all-pervading (unconscious) material cause of the universe, and purusa, the many pure conscious intelligent entities who are not subject to change. It is from the interaction of these two principles that evolution occurs.
 

The Process of the Evolution of the Universe
According to sankhya, the entire world evolves from the interaction of prakrti with purusa. This interaction does not refer to any kind of orderly conjunction, as in the contact of two finite male and female material substances. It is rather a sort of effective relationship through which prakrti is influenced by the mere presence of purusa, just as sometimes one's body is influenced or moved by the presence of a thought. Evolution cannot occur by the self (purusa) alone because the self is inactive; nor can it be initiated only by prakrti because prakrti is not conscious. The activity of prakrti must be guided by the intelligence of purusa; this cooperation between them is essential to the evolution of the universe.

Given this, two questions yet arise: how can two such different and opposing principles cooperate, and what is the interest that inspires them to interact with one another? Sankhya replies that just as a blind man and a lame man can cooperate with each other in order to get out of a forest -- by the lame man's guiding while the blind man carries him -- so do nonintelligent prakrti and inactive purusa combine with each other and cooperate to serve their purpose. What is their purpose? Prakrti requires the presence of purusa in order to be known or appreciated, and purusa requires the help of prakrti in order to distinguish itself from prakrti and thereby realize liberation. Thus, according to sankhya philosophy, the goal of the manifestation of the universe is to attain liberation. Through the interaction of purusa and prakrti, a great disturbance arises in the equilibrium in which the gunas are held prior to manifestation. In this process, raja, the active force, first becomes irritated, and through this, the two other gunas begin to vibrate. This primeval vibration releases a tremendous energy within prakrti, and the "dance" of these three energies becomes more and more dense, thus manifesting the universe in various grades and degrees. The process of manifestation originates from the unmanifested unity and completes its cycle in twenty-four stages.

The process of manifestation begins with the infusion of purusa (consciousness) into prakrti (the material cause of the universe). Metaphorically it is said that prakrti is the mother principle, and purusa is the father principle. The mother is fertilized by the father; prakrti is the soil in which consciousness can take root. Thus prakrti, the material cause of all existence, embodies consciousness.
 

Sankhya's Twenty-three Evolutes of Prakrti

Mahat or Buddha
The first evolute of prakrti is mahat or buddhi, the intellect. This is the great seed of the vast universe -- therefore the name, mahat, which means "great one." This is the state of union of purusa and prakrti. Though prakrti is unconscious material substance, it seems to be conscious and realizes itself as conscious because of the presence of the conscious self. Mahat is the state in which prakrti receives light from purusa, the fountain of light, and sees itself; and this process of seeing is the beginning of the manifestation of the universe. The individual counterpart of this cosmic state, mahat, is called buddhi, the intellect, the finest aspect of a human being that has the capacity to know the entire personality in its full purity. Buddhi is the immediate effect of prakrti resulting from the guidance of purusa; therefore buddhi is the evolute closest to purusa. Buddhi is manifested from the sattvic aspect of prakrti because the nature of sattva -- weightlessness, clarity, and light -- is affected sooner by the active force of manifestation than would be the heavy and unclear nature of tamas. Because of the sattvic quality of buddhi, the light of the self reflects in the intellect similarly to the way an external object reflects in the clear surface of a mirror. The self, seeing its reflection in the mirror of buddhi, identifies itself with the reflected image and forgets its true nature. Thus the feeling of "I-ness" is transmitted to buddhi. In this way the unconscious buddhi starts functioning as a conscious principle.

According to the sankhya system, buddhi possesses the following eight qualities: virtue (dharma); knowledge (jnana); detachment (vairagya); excellence (aisvarya); nonvirtue (adharma); ignorance (ajnana); attachment (avairagya); and imperfection or incompetency (anaisvarya). The first four are sattvic forms of buddhi, while the last four are overpowered by inertia (tamas). All of its attributes except knowledge bind prakrti and involve the self in buddhi, thereby entangling it in worldly concerns and miseries. The pure self falsely identifies with buddhi and thereby thinks it is experiencing what buddhi is experiencing. But through the use of the buddhi's eighth attribute, knowledge, it reflects pure and well-filtered knowledge onto purusa from its mirror, and purusa comes to realize its false identification with buddhi's objects and to recognize its transcendent nature in all its purity. Thus buddhi, the discriminating or decision-making function, stands nearest to the self and functions directly for the self, enabling it to discriminate between itself and prakrti and thereby achieve realization of its liberated nature.
 

Ahankara: The Sense of "I"
Ahankara is a derivative of mahat or buddhi; it is the mundane property of individuation that generates a material boundary of "I-ness." This false sense of identity separates one's self from all others and focuses it upon matter, leading a person to think, "I am this body, this is mine, and this is for me." There are three categories of ahankara -- sattvika, rajasa and tamasa -- determined by which of the three gunas is predominant in ahankara. Eleven senses arise from the sattvika ahankara: the five senses of perception (hearing, touching, seeing, tasting, and smelling), the five senses of action (verbalization, apprehension, locomotion, excretion, and procreation), and the mind (manas). The five tanmatras or subtle elements (sound, touch, color, taste, and smell) are derived from the tamasa ahankara. The function of the rajasa ahankara is to motivate the other two gunas, and thus it is the cause of both aspects of creation: the eleven senses and the five tanmatras.

This explanation of the manifestation of ahankara is based on the Sankhya-karika, the major text of sankhya philosophy (see chart above). The commentators of this text hold various views. Some state that the mind is the only sense derived from the sattvika ahankara, that the other ten senses are derived from the rajasa ahankara, and that the five subtle elements are derived from the tamasa ahankara. Irrespective of the origin of the senses, all the scholars view the nostrils, tongue, eyes, skin, and ears as the physical organs that are the sheaths of the cognitive senses. Likewise, the mouth, arms, legs, and the organs of excretion and reproduction correspond to the five senses of action -- verbalization, apprehension, locomotion, excretion, and procreation. These physical organs are not the senses; rather, they are given power by the senses. Thus the senses cannot be perceived but can only be inferred from the actions of the physical organs powered by them. The mind, the ego, and the intellect are called the internal senses, while the five cognitive senses and five senses of action are called external. The mind is master of all the external senses, and without its direction and guidance, they could not function. The mind is a very subtle sense indeed, but it also has many aspects, and it therefore comes into contact with several senses at the same time. According to sankhya philosophy, the mind is neither atomic nor eternal, but it is rather a product of prakrti and is therefore subject to origin and dissolution. The cognitive senses contact their objects and supply their experiences to the mind, which then interprets the data as desirable or undesirable perceptions. In turn, ahankara attaches itself to the objects of perception, identifying itself with the desirable ones and resenting the undesirable ones. The intellect then decides how to deal with those external objects.

The five tanmatras of sound, touch, color, taste, and smell are the subtle counterparts to the gross elements; they can be inferred but not perceived. They evolve after the ten senses have come into being and they are the cause of the five gross elements, which are derived in a gradual step-by-step process. First to evolve is the tanmatra that is the essence of sound (sabda), from which in turn ether (akasa), the space element, is derived. Therefore, the space element contains the quality of sound, which is perceived by the ear. The air element is the derivation of the essence of touch (sparsa tanmatra), which combines with that of sound. Therefore, the air element contains the attributes of sound and touch, although touch is the special quality of air and is sensed by the skin. The fire element is derived from the essence of color (rupa tanmatra). It combines the qualities of sound, touch, and co]or, and its special property is sight, which is sensed by the eyes. The water element is derived from the essence of taste (rasa tanmatra). All three preceding qualities -- sound, touch, and color -- are found in it, as well as its special quality, taste, which is sensed by the tongue. The essence of smell (gandha tanmatra) produces the earth element, whose special property is odor, which is sensed by the nostrils. This grossest element contains all of the four previous qualities.

Thus the course of evolution takes place in twenty-four stages. It starts from the root cause, prakrti, and it ends with the earth element, the grossest manifestation. This process is broken down into two major categories: the development of prakrti as buddhi, ahankara, and the eleven senses, and the evolution of the five subtle elements and five gross elements.

The first category is divided again into two parts: the internal senses (antahkarana) and the external senses (bahyakarana), which are the five cognitive and five active senses, respectively. The second category is also divided into two main parts: nonspecific qualities (avisesa) and specific qualities (visesa). The five tanmatras, or subtle elements are said to be nonspecific because they cannot be perceived and enjoyed by ordinary beings. But the five gross elements are said to be specific because whey possess specific characteristics of being pleasurable, painful, or stupefying. These specific manifestations can be categorized into two major parts: the external gross elements, and the three bodies -- physical, subtle, and causal.
 

The Sources of Valid Knowledge
Sankhya philosophy accepts only three independent sources of valid knowledge: perception, inference, and testimony. Included within these three are other sources of knowledge such as comparison, postulation, and non cognition, which are therefore not recognized as separate sources of knowledge. According to sankhya, there are three factors present in all valid knowledge: pramata, the subject; prameya, the object and pramana, the medium. Pramata is a conscious principle that receives and recognizes knowledge. It is none other than the self, pure consciousness. Prameya is the object of knowledge that is presented to the self. Pramana is the modification of the intellect through which the self comes to know an object; thus it is the source or the medium of knowledge. Valid knowledge is therefore the reflection of the self in the intellect which is modified into the form of an object.

The sankhya concept of perception (pratyaksa) as a source of valid knowledge is different from those posited by other systems of Vedic philosophy. In sankhya, valid knowledge means a definite and unerring cognition that is illuminated or made known by the self through its reflected light in buddhi. The mind, intellect, and senses are unconscious material entities and therefore cannot perceive or experience any object. For perception or experience, consciousness is needed, and consciousness belongs only to the self. But the self cannot directly apprehend the objects of the world because the self is niskriya, meaning "motionless" or "without action," and without motion or activity apprehension is not possible. If consciousness alone could apprehend the objects of the world, then, because the self is infinite and ever-present, one would know all the objects of the world. But this is not the case. The self knows objects only through the mind, intellect, and senses. True knowledge of an external object is attained when the impression of the object is perceived through the senses and reworded in the intellect, which then reflects the light of consciousness onto those objects. Perception is the direst cognition of an object through the contact of the senses. When an object, such as a hair, comes within the range of vision, there is contact between the chair and the eyes. The impression of the chair is produced in the eyes, and that impression is then analyzed and synthesized by the mind. Through the activity of the mind, the intellect then becomes modified and transformed into the form of the chair. The predominance of sattva in the intellect enables it to reflect the modification of the chair in the self. It is then reflected back to the intellect. Thus the unconscious intellect, which is modified by the object chair, becomes illumined into a conscious state in which perception is possible. Just as a mirror reflects the light of a lamp and therefore illuminates other objects, so the intellect, an unconscious principle, reflects the consciousness of the self and recognizes objects.

Two major proponents of the sankhya theory of reflectionism -- Vijnanabhiksu and Vacaspati Misra -- hold differing views. According to Vijnanabhiksu, the knowledge of an object takes place when there is a reciprocal reflection of the self in the intellect (the intellect having been modified into the form of the object) and of the intellect in the self. The senses contact the object and supply the impression of it to the mind, which transmits this impression to the intellect. The intellect then becomes modified by the object, but because the intellect is unconscious substance, it cannot analyze the experience of the object by itself. Its predominance by sattva guna, however, enables the intellect to be reflected in the self, and the self is in turn also reflected in the mirror of the intellect, which contains the modification of the object. In this way, the intellect then experiences the object. This theory of reflectionism is also accepted by Vyasa in his commentary on the Yoga-sutras.

According to the second view, held by Vacaspati Misra, perception is a process of one-sided reflection: There is a reflection of the self in the intellect, but there is no reflection of the intellect back into the self. He maintains that an object comes into contact with the senses, that its impression reaches the mind, that it is transmitted to the intellect, and that the intellect then becomes modified into the form of that object. It is at this stage that the ever-radiating light of the self illuminates the clean sattvic mirror of the intellect, which reflects the same light onto the object. The intellect then experiences the object as if the intellect were a conscious being. The intellect is just like a mirror that reflects the light of a lamp and itself becomes capable of illuminating other objects as well. This means that the intellect, but not the self, experiences the pain, pleasure, or neutrality of worldly objects, while according to Vijnanabhiksu, the pleasure, pain, and indifference are experienced by the self because the self and the intellect are reflecting each other.

Both of these views are possible within the major theory of reflectionism because the self's experience of external objects, or pain and pleasure, depends on the intensity of its identification with the intellect. One-sided reflection and reciprocal reflection are both valid views because whatever comes to the intellect is experienced by the self. A self-created state of oneness between the self and the intellect exists, but if the identification is loosened a bit, then the consciousness radiating from the self allows the intellect to appear as though it were conscious, and thus the intellect experiences the external object. The more the identification is loosened, the more the intellect experiences and the more the self watches the experiencing intellect as a witness.

Sankhya recognizes two kinds of perception: indeterminate and determinate. The first is called alocana, which means "merely seeing the object." It arises at the moment of contact between the senses and the object and is antecedent to all mental analyses and syntheses of sensory data. In this state there is recognition of the object as a mere "something" without any recognition of it as a specific object. Determinate perception, in contrast, is the result of the analysis, synthesis, and interpretation of sensory data by the mind. This type of perception is called vivecana, meaning "interpretation of the object," because it is the determinate cognition of an object as a particular identifiable thing.
 

Inference
Knowledge derived through the universal or invariable relationship between two things is called anumana (inference). The sankhya concept of inference is slightly different from that held by nyaya philosophy. In sankhya, inference is of two kinds: vita and avita. Vita is based on a universal affirmative proposition and avita is based on a universal negative proposition. Vita, positive inference is of two types: purvavat and samanyatodrsta. Purvavat inference is based on previously observed uniform concomitance between two things. For example, one can infer the existence of fire from the existence of smoke because one has already observed that smoke is always accompanied by fire. Samanyatodrsta inference is not based on any previously observed concomitance between the middle and major terms (see the nyaya chapter for an explanation of the terms of inference). This type of inference does, however, require facts that are uniformly related to the middle and major terms. For example, how can we know that we have senses? One cannot perceive his senses because they are beyond their own reach, so one must accept the existence of the senses by inference. Their existence can be inferred in the following way: for all action, some kind of instrument is needed; seeing, hearing, smelling, tasting, and touching are actions that must have their corresponding instruments; the senses are these instruments.

Negative inference, avita, is explained in the nyaya system as sesavat, in which an inference results by the elimination of all other possible alternatives. For example, a certain whole number is inferred to be two because it has been determined that it is not three or more, nor is it one or less. Yet it is a certain positive integer; therefore, it is two.
 

Testimony
Testimony (sabda) is the third source of valid knowledge. Sankhya holds the same view of sabda as nyaya, and so the reader is referred to the discussion of this subject in the chapter on nyaya.
 

The Concept of Liberation
According to sankhya philosophy, the universe is full of pain and misery, and even what is thought of as pleasure is mingled with sorrow because all pleasures ultimately end in disappointment, which is the basis of misery. It is the natural inclination of all living beings to rid themselves of pain and misery, but sankhya states that this can be achieved only through the correct discriminative knowledge of reality.

The entire external world and all internal phenomena belong to prakrti, but pure consciousness, purusa, is free from the limitations of space, time, and causation. All activity, change, thought, feeling, pain, and pleasure belong to the body/mind organism, not to the self. The self is pure ever-illumined consciousness that transcends the entire phenomenal world, including the body / mind complex. The self has a body, but the body is not the self. In the same way, the self has a mind, ego, and intellect, but it is quite distinct from all of these. Pleasure and pain, virtue and vice, merit and demerit do not color the pure self; they color the intellect as it becomes involved with its surroundings. All the experiences of the phenomenal world are received by purusa because of its false identification with the mind, intellect, and ego. The intellect is responsible for all experiences, but whenever purusa ignorantly identifies itself with the intellect, it thinks it experiences as the intellect does, even though purusa is actually always and forever beyond the evolutes of prakrti.

The manifestation of the universe into the twenty-three evolutes of prakrti is not meant to create bondage for purusa but rather to help purusa realize that it is free and distinct from prakrti. Although it may seem that external objects are meant for physical, mental, or internal enjoyment, that is not really the case because the mind, ego, and intellect do not function for themselves; they exist to provide experiences to purusa. Feelings of pain and misery are experienced because purusa falsely identifies with rajas and tamas and forgets its capacity to see through its false identification. Thus, also, purusa fails to use prakrti's sattvic manifestations as efficient instruments for discriminating the self from the non-self. The predominance of rajas and tamas in the mind, ego, and intellect does not allow these instruments to filter external experiences properly, so purusa receives unfiltered, contaminated experiences and ignorantly thinks it is suffering the pain and misery reflected by the intellect.

Sankhya views prakrti as a compassionate mother that provides everything to purusa that he needs to understand his true nature distinct from prakrti in her manifested and unmanifested states. Prakrti manifests herself out of compassion for purusa, just as a mother's milk is produced out of compassion for her child. Unless it is somehow contaminated, the milk from the mother's breast is always healthful to the child, and likewise the evolutes of prakrti are healthful to purusa unless they are contaminated by the predominance of rajas and tamas, false identification, selfish action, possessiveness, or lack of discrimination.

Both prakrti and purusa are infinite and eternal, and when prakrti is in her unmanifested state, she is so intermingled with purusa that he becomes anxious to realize his own true nature. purusa's anxiety allows him to come even closer to prakrti, and it is this move or intention toward her that inspires the latent forces in prakrti to function. Thus purusa initiates the manifestation of the universe, and thus prakrti helps purusa realize himself as distinct from her. But when through ignorance purusa forgets his purpose in coming closer to prakrti, then instead of discriminating himself from the unconscious principle, he entangles himself with it. The moment he remembers his purpose and discriminates himself from this manifest world and from its cause, he realizes his true nature and recognizes his freedom. Just as a chef continues cooking until the food is cooked and stops the moment it is ready, so purusa continues to flow in the current of life until his purpose is fulfilled. The moment the highest goal of life -- realization -- is attained, he stops flowing in that current. Likewise, a dancer performing to entertain her audience continues to dance until the audience is satisfied. The moment the course of dance (which depends on the audience's duration of enjoyment) is fulfilled, the dancer stops her dance. In the same way, the great dancer prakrti continues her dance until her discriminating function is accomplished. The moment she accomplishes her job she withdraws herself back into her unmanifested state. The purpose of the manifestation of prakrti is to show herself to purusa so he can realize that he is distinct from her. The moment purusa realizes that he is not the external objects, then the entire manifestation is withdrawn.

In actuality, pure consciousness, purusa, is subject neither to bondage nor to liberation, because he is never really in bondage. The concepts of bondage and liberation, pain and suffering, are the result of ignorance or false understanding. Prakrti binds herself with the rope of her own manifestation, and when purusa recognizes her as distinct from him, she liberates herself. As has previously been stated, there are eight attributes of mahat or buddhi (the intellect), which is the prime evolute of prakrti. These eight are attachment and detachment, vice and virtue, nonmeritorious and meritorious actions, and ignorance and knowledge. Prakrti binds herself with the first seven attributes and liberates herself with the eighth -- the light of knowledge. Thus bondage and liberation are both concepts of the intellect. Through the practice of the yoga of discrimination -- that is, the repeated affirmation of nonidentification with the body, senses, or mind (such as, for instance, "I am not the experiencer, I am not the doer; whatever is going on is in prakrti") -- one polishes one's intellect and becomes more consciously aware of one's true nature. This type of knowledge or understanding leads one to the state of freedom from all confusions and false identifications, and thus one attains the knowledge of the true self. After the self realizes its true nature, all anxieties are dissolved. Then the self becomes disinterested in seeing prakrti, and prakrti becomes disinterested in showing herself, because she has seen and her purpose has been fulfilled. Prakrti and purusa are both infinite and all-pervading and are therefore eternally together, like two sides of the same coin, but when their purpose is fulfilled the process of manifestation ceases.

In the sankhya philosophy, there are two kinds of liberation: jivana mukti and videha mukti. The liberation attained in one's lifetime is called jivana mukti. In this kind of liberation, a person continues his existence on this platform as a liberated being. He lives in this world and enjoys the worldly objects until he casts off his body. He continues his journey through worldly life just as a fan continues to revolve, due to its previously generated speed, for a short while after it has been switched off. When all the samskaras -- the impressions of past actions -- are finished, then he casts off his body and is said to enter into videha mukti, which is liberation after death.
 

The Concept of God
The earliest available text of Nirisvara sankhya, the Sankhya-karika, does not discuss the existence of God at all. The absence of any reference to God led the proponents of this system to conclude that the early sankhya philosophers did not accept the existence of God. They argued that because the entire universe is a system of cause and effect, it could not be caused by God because by definition God is eternal and immutable. That which is unchanging cannot be the active cause of anything, so the ultimate cause of the universe is eternal but ever-changing. That cause is prakrti, the eternal and ever-changing unconscious material principle. In reply to this, one could argue that prakrti is not intelligent and must, therefore, be controlled and directed by some intelligent principle in order to produce the universe. But because there are many purusas, they cannot guide and lead the infinite, all-pervading prakrti, so one must therefore conclude that there is a God. But this is not possible, the proponents of nontheistic sankhya reply, because the act of controlling or guiding prakrti means to do something or to be active. In addition, if God controls prakrti, then what inspires God to make her create a world full of pain and misery? Moreover, one cannot say that God has desires because desire implies imperfection, which is a quality God cannot have. Therefore, there is no such thing as God. purusa is sufficient to inspire the unconscious prakrti to manifest herself in the form of the universe.

Later, a section of sankhya philosophers were persuaded to accept the existence of God. In debates with theistic opponents they found it very difficult to explain the creation without including a Supreme Being in their system. One logical weakness of Nirisvara sankhya that was attacked by theists is the belief in many purusas but only one prakrti. Was it one purusa or all the purusas together that inspired prakrti to manifest? If only one, then creation occurred against the wish of the other purusas. Why did the desire of only one soul implicate all others in birth and death? If all the purusas together inspired prakrti to create, then there must be some communication and agreement among the purusas. But there is no record of a cosmic conference of all the purusas to make such a decision. Therefore, there must be one Supreme Being who guides prakrti independently.