Patañjali's Yoga Sūtras (approximately 2nd century BCE – 4th century CE) open with one of the most precise definitions in the entire tradition: yogaś citta-vṛtti-nirodhaḥ — "Yoga is the cessation of the fluctuations of the mind" (YS 1.2). Everything else in the Yoga Sūtras is an elaboration of this definition: what the fluctuations are, why they arise, and the systematic path by which they are brought to cessation.
The eight limbs — Aṣṭāṅga Yoga (YS 2.28–2.29)
1
Yama
The five ethical restraints: non-violence (ahiṃsā), truthfulness (satya), non-stealing (asteya), continence (brahmacarya), non-possessiveness (aparigraha)
2
Niyama
The five personal observances: purity (śauca), contentment (santoṣa), austerity (tapas), self-study (svādhyāya), surrender to Īśvara (Īśvara-praṇidhāna)
3
Āsana
Steady, comfortable posture — originally the seated meditation posture, not a system of physical exercises. In the Yoga Sūtras āsana occupies just three sūtras (2.46–2.48) and is defined simply as a stable, relaxed seat.
4
Prāṇāyāma
Regulation of the breath — interrupting the normal rhythm of inhalation and exhalation to calm the nervous system and prepare the mind for deeper concentration
5
Pratyāhāra
Withdrawal of the senses from their objects — the transition from the external limbs (Yama through Prāṇāyāma) to the internal limbs. The senses cease to follow their objects and turn inward
6
Dhāraṇā
Concentration — fixing the mind on a single point or object (an image, a mantra, a part of the body, the breath) for a sustained period
7
Dhyāna
Meditation — the continuous, unbroken flow of the mind toward the object of concentration. Distinguished from Dhāraṇā by continuity: Dhāraṇā fixes; Dhyāna flows steadily
8
Samādhi
Deep meditative absorption — the meditator, the act of meditation, and the object of meditation merge. In Samprajñāta Samādhi the object is still present; in Asamprajñāta Samādhi all mental content ceases. The culmination leading to Kaivalya.
The goal — Kaivalya
YS 2.2 and 4.34 — the purpose and the goal
samādhi-bhāvanārthaḥ kleśa-tanū-karaṇārthaś ca (YS 2.2)
"The purpose [of Kriyā Yoga] is to cultivate Samādhi and to attenuate the afflictions (Kleśas)."
puruṣārtha-śūnyānāṃ guṇānāṃ pratiprasavaḥ kaivalyaṃ svarūpa-pratiṣṭhā vā citi-śaktir iti (YS 4.34)
"Kaivalya is the return of the Guṇas to their origin, having no further purpose for the Puruṣa — or the establishment of the power of consciousness in its own nature."
Kaivalya (from kevala — alone, isolated) is the Yoga Sūtras' term for liberation. It is the Puruṣa's recognition that it has always been separate from Prakṛti — that all the Guṇas' activity was never actually the Puruṣa's own activity. When this recognition is complete and stable, the Guṇas cease to operate on behalf of the Puruṣa, and the Puruṣa rests in its own pure consciousness. This is a Sāṃkhya-based liberation — distinct from the Vedāntic Mokṣa of recognising Brahman, though the two are often conflated in modern practice.
Rāja Yoga vs Haṭha Yoga
The modern global yoga tradition is primarily Haṭha Yoga — a tradition focused on physical postures (āsanas), breathing exercises (prāṇāyāma), and purification practices, developed in texts like the Haṭhapradīpikā (15th century CE). Rāja Yoga (Patañjali's system) and Haṭha Yoga are distinct traditions that were later synthesised. The Haṭhapradīpikā itself describes its practices as preparatory for Rāja Yoga — using the body as the instrument for attaining the mental control that Patañjali describes. Modern global āsana practice (as in Iyengar, Ashtanga, Vinyasa yoga) derives primarily from the Haṭha tradition, not directly from Patañjali's Yoga Sūtras. Source: De Michelis, A History of Modern Yoga (Continuum, 2004); Singleton, Yoga Body (OUP, 2010).
The five Kleśas — afflictions that generate bondage
The Yoga Sūtras' analysis of the causes of suffering is one of the most precise in the tradition. YS 2.3–2.9 names five Kleśas (afflictions): Avidyā (ignorance — the root), Asmitā (ego-sense — misidentifying the Puruṣa with the mind), Rāga (attraction — clinging to pleasure), Dveṣa (aversion — pushing away pain), and Abhiniveśa (will to live — the deeply instinctive fear of death). These five are not merely psychological states but the deep structures of conditioned experience that keep the Puruṣa entangled with Prakṛti. The eight-limbed path is designed to progressively attenuate all five, from Avidyā (the root) through the others. Source: Bryant (trans.), Yoga Sūtras of Patañjali (North Point, 2009), pp. 161–209.
Īśvara-praṇidhāna — surrender to Īśvara
Among the five Niyamas (personal observances), Īśvara-praṇidhāna (surrender to Īśvara) stands out as the most devotional element of Patañjali's otherwise primarily technical system. YS 1.23–1.26 introduces Īśvara as "a special Puruṣa untouched by afflictions, actions, their results, and the latent impressions" — and states that from dedication to Īśvara, Samādhi is attained. In Vyāsa's commentary (the primary Yoga Bhāṣya), this becomes Bhakti within the Rāja Yoga framework — a point of convergence between the meditative path and the devotional path. Source: Bryant (2009), pp. 77–100; Desikachar, The Heart of Yoga (Inner Traditions, 1999).
Kaivalya vs Mokṣa — the two liberations
The Yoga Sūtras' Kaivalya and the Vedāntic Mokṣa are formally distinct liberation concepts, reflecting the different ontological frameworks of their home traditions. In the Sāṃkhya-Yoga framework, Puruṣa (pure consciousness) and Prakṛti (matter-energy, including the mind) are eternally distinct realities. Kaivalya is the Puruṣa's recognition of this eternal distinctness — it has never been entangled with Prakṛti; what appeared to be entanglement was a case of mistaken identity. Liberation = the correction of this mistaken identity, after which the Puruṣa abides in its own nature (svarūpa-pratiṣṭhā).
In the Advaita Vedāntic framework, there is no irreducible duality between Ātman and Brahman — the apparent distinction is itself the product of Avidyā, and Mokṣa is the recognition that Ātman IS Brahman. This is a fundamentally different liberating recognition: not "I am not this" (Kaivalya) but "I am that" (Mokṣa). Vivekananda's synthesis of the four paths glossed over this difference, treating Kaivalya and Mokṣa as equivalent — which has generated considerable confusion in the modern yoga and Vedānta worlds. Source: Bryant (2009), Introduction; De Michelis (2004), Ch.5; Feuerstein, The Yoga Tradition (Hohm, 2001).