The world is maintained to be real, and that from all eternity; for the existent can only be produced from the existent. The reality of an object is regarded as resulting simply from perception, always supposing the senses of the perceiver to be sound. The world is described as developing according to certain laws out of primitive matter (prakṛiti or pradhāna). The genuine philosophic spirit of its method of rising from the known elements of experience to the unknown by logical demonstration till the ultimate cause is reached, must give this system a special interest in the eyes of evolutionists whose views are founded on the results of modern physical science.

The evolution and diversity of the world are explained by primæval matter, although uniform and indivisible, consisting of three different substances called guṇas or constituents (originally “strands” of a rope). By the combination of these in varying proportions the diverse material products were supposed to have arisen. The constituent, called sattva, distinguished by the qualities of luminousness and lightness in the object, and by virtue, benevolence, and other pleasing attributes in the subject, is associated with the feeling of joy; rajas, distinguished by activity and various hurtful qualities, is associated with pain; and tamas, distinguished by heaviness, rigidity, and darkness on the one hand, and fear, unconsciousness, and so forth, on the other, is associated with apathy. At the end of a cosmic period all things are supposed to be dissolved into primitive matter, the alternations of evolution, existence, and dissolution having neither beginning nor end.

The psychology of the Sānkhya system is specially important. Peculiarly interesting is its doctrine that all mental operations, such as perception, thinking, willing, are not performed by the soul, but are merely mechanical processes of the internal organs, that is to say, of matter. The soul itself possesses no attributes or qualities, and can only be described negatively. There being no qualitative difference between souls, the principle of personality and identity is supplied by the subtile or internal body, which, chiefly formed of the inner organs and the senses, surrounds and is made conscious by the soul. This internal body, being the vehicle of merit and demerit, which are the basis of transmigration, accompanies the soul on its wanderings from one gross body to another, whether the latter be that of a god, a man, an animal, or a tree. Conscious life is bondage to pain, in which pleasure is included by this peculiarly pessimistic system. When salvation, which is the absolute cessation of pain, is obtained, the internal body is dissolved into its material elements, and the soul, becoming finally isolated, continues to exist individually, but in absolute unconsciousness.

The name of the system, which only begins to be mentioned in the later Upanishads, and more frequently in the Mahābhārata, is derived from saṃkhyā, “number.” There is, however, some doubt as to whether it originally meant “enumeration,” from the twenty-five tattvas or principles which it sets forth, or “inferential or discriminative” doctrine, from the method which it pursues.

Kapila, the founder of the system, whose teaching is presupposed by Buddhism, and whom Buddhistic legend connects with Kapila-vastu, the birthplace of Buddha, must have lived before the middle of the sixth century. No work of his, if he ever committed his system to writing, has been preserved. Indeed, the very existence of such a person as Kapila has been doubted, in spite of the unanimity with which Indian tradition designates a man of this name as the founder of the system. The second leading authority of the Sānkhya philosophy was Panchaçikha, who may have lived about the beginning of our era. The oldest systematic manual which has been preserved is the Sānkhya-kārikā of Īçvara-kṛishṇa. As it was translated into Chinese between 557 and 583 A.D., it cannot belong to a later century than the fifth, and may be still older. This work deals very concisely and methodically with the doctrines of the Sānkhya in sixty-nine stanzas (composed in the complicated Āryā metre), to which three others were subsequently added. It appears to have superseded the Sūtras of Panchaçikha, who is mentioned in it as the chief disseminator of the system. There are two excellent commentaries on the Sānkhya-kārikā, the one composed about 700 A.D. by Gauḍapāda, and the other soon after 1100 A.D. by Vāchaspati Miçra.

The Sānkhya Sūtras, long regarded as the oldest manual of the system, and attributed to Kapila, were probably not composed till about 1400 A.D. The author of this work, which also goes by the name of Sānkhya-pravachana, endeavours in vain to show that there is no difference between the doctrines of the Sānkhya and of the Upanishads. He is also much influenced by the ideas of the Yoga as well as the Vedānta system. In the oldest commentary on this work, that of Aniruddha, composed about 1500 A.D., the objectiveness of the treatment is particularly useful. Much more detailed, but far less objective, is the commentary of Vijnāna-bhikshu, entitled Sānkhya-pravachana-bhāshya, and written in the second half of the sixteenth century. The author’s point of view being theistic, he effaces the characteristic features of the different systems in the endeavour to show that all the six orthodox systems contain the absolute truth in their main doctrines.

From the beginning of our era down to recent times the Sānkhya doctrines have exercised considerable influence on the religious and philosophical life of India, though to a much less extent than the Vedānta. Some of its individual teachings, such as that of the three guṇas, have become the common property of the whole of Sanskrit literature. At the time of the great Vedāntist, Çankara (800 A.D.), the Sānkhya system was held in high honour. The law book of Manu followed this doctrine, though with an admixture of the theistic notions of the Mīmāṃsā and Vedānta systems as well as of popular mythology. The Mahābhārata, especially Book XII., is full of Sānkhya doctrines; indeed almost every detail of the teachings of this system is to be found somewhere in the great epic. Its numerous deviations from the regular Sānkhya text-books are only secondary, as Professor Garbe thinks, even though the Mahābhārata is our oldest actual source for the system. Nearly half the Purāṇas follow the cosmogony of the Sānkhya, and even those which are Vedāntic are largely influenced by its doctrines. The purity of the Sānkhya notions are, however, everywhere in the Purāṇas obscured by Vedānta doctrines, especially that of cosmical illusion. A peculiarity of the Purāṇic Sānkhya is the conception of Spirit or Purusha as the male, and Matter or Prakṛiti as the female, principle in creation.

On the Sānkhya system are based the two philosophical religions of Buddhism and Jainism in all their main outlines. Their fundamental doctrine is that life is nothing but suffering. The cause of suffering is the desire, based on ignorance, to live and enjoy the world. The aim of both is to redeem mankind from the misery of mundane existence by the annihilation of desire, with the aid of renunciation of the world and the practice of unbounded kindness towards all creatures. These two pessimistic religions are so extremely similar that the Jainas, or adherents of Jina, were long looked upon as a Buddhist sect. Research has, however, led to the discovery that the founders of both systems were contemporaries, the most eminent of the many teachers who in the sixth century opposed the Brahman ceremonial and caste pretensions in Northern Central India. Both religions, while acknowledging the lower and ephemeral gods of Brahmanism, deny, like the Sānkhya, the existence of an eternal supreme Deity. As they developed, they diverged in various respects from the system to which they owed their philosophical notions. Hence it came about that Sānkhya writers stoutly opposed some of their teachings, particularly the Buddhist denial of soul, the doctrine that all things have only a momentary existence, and that salvation is an annihilation of self. Here, however, it should be noted that Buddha himself refused to decide the question whether nirvāṇa is complete extinction or an unending state of unconscious bliss. The latter view was doubtless a concession to the Vedāntic conception of Brahma, in which the individual soul is merged on attaining salvation.

The importance of these systems lies not in their metaphysical speculations, which occupy but a subordinate position, but in their high development of moral principles, which are almost entirely neglected in the orthodox systems of Indian philosophy. The fate of the two religions has been strangely different. Jainism has survived as an insignificant sect in India alone; Buddhism has long since vanished from the land of its birth, but has become a world religion counting more adherents than any other faith.

The Sānkhya philosophy, with the addition of a peculiar form of mental asceticism as the most effective means of acquiring saving knowledge, appears to have assumed definite shape in a manual at an earlier period than any of the other orthodox systems. This is the Yoga philosophy founded by Patanjali and expounded in the Yoga Sūtras. The priority of this text-book is rendered highly probable by the fact that it is the only philosophical Sūtra work which contains no polemics against the others. There seems, moreover, to be no sufficient ground to doubt the correctness of the native tradition identifying the founder of the Yoga system with the grammarian Patanjali. The Yoga Sūtras therefore probably date from the second century B.C. This work also goes by the name of Sānkhya-pravachana, the same as that given to the later Sānkhya Sūtras, a sufficiently clear proof of its close connection with Kapila’s philosophy. In the Mahābhārata the two systems are actually spoken of as one and the same.