Classical yoga incorporates epistemology, metaphysics, ethical practices, systematic exercises and self-development techniques for body, mind and spirit.[144] Its epistemology (pramana) and metaphysics is similar to that of the Sāṅkhya school. The metaphysics of Classical Yoga, like Sāṅkhya, is mainly dualistic, positing that there are two distinct realities. These are prakriti (nature), which is the eternal and active unconscious source of the material world and is composed of three gunas, and the puruṣas (persons), the plural consciousnesses which are the intelligent principles of the world, and are multiple, inactive and eternal witnesses. Each person has a individual puruṣa, which is their true self, the witness and the enjoyer, and that which is liberated. This metaphysical system holds that puruṣas undergo cycles of reincarnation through its interaction and identification with prakirti. Liberation, the goal of this system, results from the isolation (kaivalya) of puruṣa from prakirti, and is achieved through a meditation which detaches oneself from the different forms (tattvas) of prakirti.[243] This is done by stilling one's thought waves (citta vritti) and resting in pure awareness of puruṣa.

Description of an early form of yoga called nirodhayoga (yoga of cessation) is contained in the Mokshadharma section of the 12th chapter (Shanti Parva) of the Mahabharata (third century BCE).[109] Nirodhayoga emphasizes progressive withdrawal from the contents of empirical consciousness such as thoughts, sensations etc. until purusha (Self) is realized. Terms like vichara (subtle reflection), viveka (discrimination) and others which are similar to Patanjali's terminology are mentioned, but not described.[110] There is no uniform goal of yoga mentioned in the Mahabharata. Separation of self from matter, perceiving Brahman everywhere, entering into Brahman etc. are all described as goals of yoga. Samkhya and yoga are conflated together and some verses describe them as being identical.[111] Mokshadharma also describes an early practice of elemental meditation.[112] Mahabharata defines the purpose of yoga as the experience of uniting the individual ātman with the universal Brahman that pervades all things.[111]
^ The Pāli and Sanskrit word bhāvanā literally means "development" as in "mental development." For the association of this term with "meditation," see Epstein (1995), p. 105; and, Fischer-Schreiber et al. (1991), p. 20. As an example from a well-known discourse of the Pali Canon, in "The Greater Exhortation to Rahula" (Maha-Rahulovada Sutta, MN 62), Ven. Sariputta tells Ven. Rahula (in Pali, based on VRI, n.d.): ānāpānassatiṃ, rāhula, bhāvanaṃ bhāvehi. Thanissaro (2006) translates this as: "Rahula, develop the meditation [bhāvana] of mindfulness of in-&-out breathing." (Square-bracketed Pali word included based on Thanissaro, 2006, end note.)
The chronology of completion of these yoga-related Early Buddhist Texts, however, is unclear, just like ancient Hindu texts.[85][86] Early known Buddhist sources like the Majjhima Nikāya mention meditation, while the Anguttara Nikāya describes Jhāyins (meditators) that resemble early Hindu descriptions of Muni, Kesins and meditating ascetics,[87] but these meditation-practices are not called yoga in these texts.[88] The earliest known specific discussion of yoga in the Buddhist literature, as understood in modern context are from the later Buddhist Yogācāra and Theravada schools.[88]
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The Gita consists of 18 chapters and 700 shlokas (verses),[118] with each chapter named as a different yoga, thus delineating eighteen different yogas.[118][119] Some scholars divide the Gita into three sections, with the first six chapters with 280 shlokas dealing with Karma yoga, the middle six containing 209 shlokas with Bhakti yoga, and the last six chapters with 211 shlokas as Jnana yoga; however, this is rough because elements of karma, bhakti and jnana are found in all chapters.[118]
^ "application or concentration of the thoughts, abstract contemplation, meditation , (esp.) self-concentration, abstract meditation and mental abstraction practised as a system (as taught by Patañjali and called the yoga philosophy; it is the second of the two sāṃkhya systems, its chief aim being to teach the means by which the human spirit may attain complete union with īśvara or the Supreme Spirit; in the practice of self-concentration it is closely connected with Buddhism". Monier-Williams, A Sanskrit Dictionary (1899)
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The first Hindu teacher to actively advocate and disseminate aspects of yoga, not including asanas, to a western audience, Swami Vivekananda, toured Europe and the United States in the 1890s.[207] The reception which Swami Vivekananda received built on the active interest of intellectuals, in particular the New England Transcendentalists, among them Ralph Waldo Emerson (1803–1882), who drew on German Romanticism and philosophers and scholars like G. W. F. Hegel (1770–1831), the brothers August Wilhelm Schlegel (1767–1845) and Karl Wilhelm Friedrich Schlegel (1772–1829), Max Mueller (1823–1900), Arthur Schopenhauer (1788–1860), and others who had (to varying degrees) interests in things Indian.[208][209]

Some Christians integrate yoga and other aspects of Eastern spirituality with prayer and meditation. This has been attributed to a desire to experience God in a more complete way.[281] In 2013, Monsignor Raffaello Martinelli, servicing Congregation for the Doctrine of the Faith, having worked for over 23 years with Cardinal Joseph Ratzinger (Pope Benedict XVI),[282] said that for his Meditation, a Christian can learn from other religious traditions (zen, yoga, controlled respiration, Mantra), quoting Aspects of Christian meditation: "Just as "the Catholic Church rejects nothing of what is true and holy in these religions," neither should these ways be rejected out of hand simply because they are not Christian. On the contrary, one can take from them what is useful so long as the Christian conception of prayer, its logic and requirements are never obscured. It is within the context of all of this that these bits and pieces should be taken up and expressed anew."[283] Previously, the Roman Catholic Church, and some other Christian organizations have expressed concerns and disapproval with respect to some eastern and New Age practices that include yoga and meditation.[284][285][286]

Yoga gurus from India later introduced yoga to the West,[15] following the success of Swami Vivekananda in the late 19th and early 20th century with his adaptation of yoga tradition, excluding asanas.[15] Outside India, it has developed into a form of posture-based physical fitness, stress-relief and relaxation technique.[16] Yoga in Indian traditions, however, is more than physical exercise; it has a meditative and spiritual core.[16][17] One of the six major orthodox schools of Hinduism is also called Yoga, which has its own epistemology and metaphysics, and is closely related to Hindu Samkhya philosophy.[18]