In order to make his system more acceptable, Patanjali introduced into it the doctrine of a personal god, but in so loose a way as not to affect the system as a whole. Indeed, the parts of the Sūtras dealing with the person of God are not only unconnected with the other parts of the treatise, but even contradict the foundations of the system. For the final aim of man is here represented as the absolute isolation (kaivalya) of the soul from matter, just as in the Sānkhya system, and not union with or absorption in God. Nor are the individual souls here derived from the “special soul” or God, but are like the latter without a beginning.

The really distinctive part of the system is the establishment of the views prevailing in Patanjali’s time with regard to asceticism and the mysterious powers to be acquired by its practice. Yoga, or “yoking” the mind, means mental concentration on a particular object. The belief that fasting and other penances produce supernatural powers goes back to remote prehistoric times, and still prevails among savage races. Bodily asceticism of this kind is known to the Vedas under the name of tapas. From this, with the advance of intellectual life in India, was developed the practice of mental asceticism called yoga, which must have been known and practised several centuries before Patanjali’s time. For recent investigations have shown that Buddhism started not only from the theoretical Sānkhya but from the practical Yoga doctrine; and the condition of ecstatic abstraction was from the beginning held in high esteem among the Buddhists. Patanjali only elaborated the doctrine, describing at length the means of attaining concentration and carrying it to the highest pitch. In his system the methodical practice of Yoga acquired a special importance; for, in addition to conferring supernatural powers, it here becomes the chief means of salvation. His Sūtras consist of four chapters dealing with deep meditation (samādhi), the means for obtaining it (sādhana), the miraculous powers (vibhūti) it confers, and the isolation (kaivalya) of the redeemed soul. The oldest and best commentary on this work is that of Vyāsa, dating from the seventh century A.D.

Many of the later Upanishads are largely concerned with the Yoga doctrine. The lawbook of Manu in Book VI. refers to various details of Yoga practice. Indeed, it seems likely, owing to the theistic point of view of that work, that its Sānkhya notions were derived from the Yoga system. The Mahābhārata treats of Yoga in considerable detail, especially in Book XII. It is particularly prominent in the Bhagavadgītā, which is even designated a yoga-çāstra. Belief in the efficacy of Yoga still prevails in India, and its practice survives. But its adherents, the Yogīs, are at the present day often nothing more than conjurers and jugglers.

The exercises of mental concentration are in the later commentaries distinguished by the name of rāja-yoga or “chief Yoga.” The external expedients are called kriyā-yoga, or “practical Yoga.” The more intense form of the latter, in later works called haṭha-yoga, or “forcible Yoga,” and dealing for the most part with suppression of the breath, is very often contrasted with rāja-yoga.

Among the eight branches of Yoga practice the sitting posture (āsana), as not only conducive to concentration, but of therapeutic value, is considered important. In describing its various forms later writers positively revelled, eighty-four being frequently stated to be their normal number. In the haṭha-yoga there are also a number of other postures and contortions of the limbs designated mudrā. The best-known mudrā, called khecharī, consists in turning the tongue back towards the throat and keeping the gaze fixed on a point between the eyebrows. Such practices, in conjunction with the suppression of breath, were capable of producing a condition of trance. There is at least the one well-authenticated case of a Yogī named Haridās who in the thirties wandered about in Rājputāna and Lahore, allowing himself to be buried for money when in the cataleptic condition. The burial of the Master of Ballantrae by the Indian Secundra Dass in Stevenson’s novel was doubtless suggested by an account of this ascetic.

In contrast with the two older and intimately connected dualistic schools of the Sānkhya and Yoga, there arose about the beginning of our era the only two, even of the six orthodox systems of philosophy, which were theistic from the outset. One of them, being based on the Vedas and the Brāhmaṇas, is concerned with the practical side of Vedic religion; while the other, alone among the philosophical systems, represents a methodical development of the fundamental non-dualistic speculations of the Upanishads. The former, which has only been accounted a philosophical system at all because of its close connection with the latter, is the Pūrva-mīmāṃsā or “First Inquiry,” also called Karma-mīmāṃsā or “Inquiry concerning Works,” but usually simply Mīmāṃsā. Founded by Jaimini, and set forth in the Karma-mīmāṃsā Sūtras, this system discusses the sacred ceremonies and the rewards resulting from their performance. Holding the Veda to be uncreated and existent from all eternity, it lays special stress on the proposition that articulate sounds are eternal, and on the consequent doctrine that the connection of a word with its sense is not due to convention, but is by nature inherent in the word itself. Owing to its lack of philosophical interest, this system has not as yet much occupied the attention of European scholars.

The oldest commentary in existence on the Mīmāṃsā Sūtras is the bhāshya of Çabara Svāmin, which in its turn was commented on about 700 A.D. by the great Mīmāṃsist Kumārila in his Tantra-vārttika and in his Çloka-vārttika, the latter a metrical paraphrase of Çabara’s exposition of the first aphorism of Patanjali. Among the later commentaries on the Mīmāṃsā Sūtras the most important is the Jaiminīya-nyāya-mālā-vistara of Mādhava (fourteenth century).

Far more deserving of attention is the theoretical system of the Uttara-Mīmāṃsā, or “Second Inquiry.” For it not only systematises the doctrines of the Upanishads—therefore usually termed Vedānta, or “End of the Veda”—but also represents the philosophical views of the Indian thinkers of to-day. In the words of Professor Deussen, its relation to the earlier Upanishads resembles that of Christian dogmatics to the New Testament. Its fundamental doctrine, expressed in the famous formula tat tvam asi, “thou art that,” is the identity of the individual soul with God (brahma). Hence it is also called the Brahma- or Çārīraka-mīmāṃsā, “Inquiry concerning Brahma or the embodied soul.” The eternal and infinite Brahma not being made up of parts or liable to change, the individual soul, it is here laid down, cannot be a part or emanation of it, but is the whole indivisible Brahma. As there is no other existence but Brahma, the Vedānta is styled the advaita-vāda, or “doctrine of non-duality,” being, in other words, an idealistic monism. The evidence of experience, which shows a multiplicity of phenomena, and the statements of the Veda, which teach a multiplicity of souls, are brushed aside as the phantasms of a dream which are only true till waking takes place.

The ultimate cause of all such false impressions is avidyā or innate ignorance, which this, like the other systems, simply postulates, but does not in any way seek to account for. It is this ignorance which prevents the soul from recognising that the empirical world is mere māyā or illusion. Thus to the Vedāntist the universe is like a mirage, which the soul under the influence of desire (tṛishṇā or “thirst”) fancies it perceives, just as the panting hart sees before it sheets of water in the fata morgana (picturesquely called mṛiga-tṛishṇā or “deer-thirst” in Sanskrit). The illusion vanishes as if by magic, when the scales fall from the eyes, on the acquisition of true knowledge. Then the semblance of any distinction between the soul and God disappears, and salvation (moksha), the chief end of man, is attained.

Saving knowledge cannot of course be acquired by worldly experience, but is revealed in the theoretical part (jnāna-kāṇḍa) of the Vedas, that is to say, in the Upanishads. By this correct knowledge the illusion of the multiplicity of phenomena is dispelled, just as the illusion of a snake when there is only a rope. Two forms of knowledge are, however, distinguished in the Vedānta, a higher (parā) and a lower (aparā). The former is concerned with the higher and impersonal Brahma (neuter), which is without form or attributes, while the latter deals with the lower and personal Brahmā (masculine), who is the soul of the universe, the Lord (īçvara) who has created the world and grants salvation. The contradiction resulting from one and the same thing having form and no form, attributes and no attributes, is solved by the explanation that the lower Brahmā has no reality, but is merely an illusory form of the higher and only Brahma, produced by ignorance.