Two meanings of the word
Siddhi derives from the Sanskrit root sidh — to succeed, to bring to completion — and carries two related senses that the contemplative literature uses without always distinguishing them. In the broader sense, a siddhi is the attainment the practice was directed at: the steady recognition the sādhaka of jñāna yoga was working toward, the vairāgya the householder was cultivating, the disentanglement the Yoga Sūtras call *kaivalya*. In the narrower and more popular sense, the term refers to the supernormal capacities — clairvoyance, knowledge of past lives, levitation, the ability to read another's mind, action at a distance — that the Indian and Tibetan traditions treat as predictable byproducts of sustained inner work. The two senses are not separable in the classical literature: the tantric Mahāsiddhas the Tibetan tradition lists by name are siddhas in both senses — possessors of unusual capacities who are also realised practitioners — and the question whether the minor siddhis and the supreme siddhi (liberation itself) are different in kind or only in scope is contested across the schools.
The classical catalogue, and the classical warning
The third book of the Yoga Sūtras — the Vibhūti-pāda, the chapter on powers — is the longest single classical inventory. Patañjali names roughly twenty-five distinct capacities arising from *saṃyama* — the combined practice of dhāraṇā, dhyāna and *samādhi* — applied to specific objects: saṃyama on the transformations of states yields knowledge of past and future; on the heart yields knowledge of mind; on the sun yields knowledge of the cosmos; and so on. The classical eight mahāsiddhis the later commentary tradition extracts from the text are aṇimā (becoming infinitesimal), mahimā (becoming infinite), laghimā (becoming weightless), garimā (becoming massive), prāpti (reach), prākāmya (irresistible will), īśitva (mastery over phenomena) and vaśitva (control over the senses). The chapter that catalogues these — and Vyāsa's bhāṣya that commented on it — is unambiguous about their status: they are obstacles to samādhi, obstacles even though they are powers. The same warning recurs in the Theravāda literature (Buddhaghosa's Visuddhimagga treats the iddhi — the Pāli cognate — under the same disciplinary frame), in the Vajrayāna instructions to yidam practitioners, and across the Chinese Chán commentary. The trap is uniform across the traditions: the practitioner who reaches the depth at which the powers arise is also the practitioner most positioned to mistake them for the recognition the depth was for.
How the question shows up in the index
Sadhguru's *Inner Engineering* and the longer *Inner Engineering Online* course work inside a yogic tradition that takes the siddhis seriously as predictable phenomena while teaching the explicit Patañjali-style disregard for them. His longer-form talks treat the same distinction without naming it: Sadhguru on disability and spiritual practice and Sadhguru on unlocking the mind's full potential are unambiguous that what the practice is for is not the catalogued powers but the recognition under which the powers are insignificant. Paramahansa Yogananda's *Autobiography of a Yogi* is the index's most extended document of the siddhi literature in narrative form — the recurring encounters with figures who exhibit prāpti (the appearance of food where there was none, the multilocation of Babaji), īśitva (the saint who turns the storm aside), the jīvanmukta operating from a recognition the powers are functions of — and is also the index's clearest case-by-case demonstration of why the tradition treats the powers as ancillary: every figure who exhibits them is recorded as treating them as ancillary themselves. Nisargadatta Maharaj's *I Am That* takes the opposite tack: the recognition of the ground that the Yoga Sūtras' third chapter treats as the supreme siddhi is the only siddhi the jñāna tradition acknowledges, and the vibhūti powers are not treated except dismissively. Sadhguru's longer lectures and the Ram Dass material on Neem Karoli Baba — a teacher whose siddhis were the everyday social context of his disciples' encounters with him — show the question worked out in two different keys: the yogic one that takes the powers as ordinary phenomena, and the bhakti one that takes them as the byproduct of a devotional surrender they are not the point of.
What it isn't
Siddhi is not magic, in the sense the modern Western reader is most likely to import. The traditions that catalogue the powers also catalogue the conditions under which they arise — extended saṃyama, prāṇāyāma of a specific intensity, the depth of *samādhi* the Yoga Sūtras call nirvikalpa — and treat them as functions of the depth, not as separable abilities the practitioner can acquire and dispose of. The term is also not a metaphor for psychological growth, as the modern adaptive literature sometimes treats it: the classical texts describe the siddhis as concrete phenomena and the classical commentary works hard to distinguish them from the imagined powers of the untutored practitioner. And the siddhis are not the goal — every tradition that catalogues them says so, and every tradition that catalogues them produces literature on practitioners who lost the goal to the powers. The term is interesting in the contemporary reception chiefly because the contemporary reception is so often a partial one: either the powers are taken too literally and the warning is ignored, or the warning is taken so seriously that the literature on the powers themselves is dismissed as folklore. The classical position is that both halves are real, that the second outranks the first, and that the practitioner who has not understood the second has not yet earned the right to encounter the first.
— end of entry —