What is Buddhi?
Buddhi (Sanskrit: बुद्धि) is the discriminating intellect — the faculty of the mind that reasons, judges, and decides. The word comes from the Vedic root budh, meaning to wake, observe, and know. This is the same root as Buddha (the awakened one) and bodhi (awakening). In Sāṃkhya-Yoga philosophy, buddhi is the first and most subtle product of [prakṛti](lexicon:prakriti) — the entire phenomenal field — and it is what makes [viveka](lexicon:viveka), discriminating wisdom, possible.
Buddhi vs manas, ahaṃkāra, and citta
Indian philosophical analysis groups four inner faculties under the term antaḥkaraṇa (the inner instrument): buddhi (intellect), manas (the sense-coordinating mind), [ahaṃkāra](lexicon:ahamkara) (the I-maker), and [citta](lexicon:citta) (the reservoir of memory and impression). These are not four separate entities. They are four functions of a single inner apparatus. Manas gathers and presents input from the senses but does not judge. Ahaṃkāra refers experience to a felt self. Citta stores what has been experienced. Buddhi is the decisive faculty: it is what actually judges, determines, and resolves. It is what can, in principle, distinguish truth from falsehood and dharma from adharma.
Buddhi in Sāṃkhya-Yoga
Sāṃkhya — the oldest of the six classical Indian philosophical schools — analyses reality into twenty-five categories. Puruṣa (pure consciousness) stands alone. The other twenty-four descend from [prakṛti](lexicon:prakriti) in a fixed sequence. Buddhi is the first to emerge. The Sāṃkhya-Kārikā of Īśvarakṛṣṇa (roughly 4th–5th century CE) calls it mahat, the great one. From mahat arises [ahaṃkāra](lexicon:ahamkara), and from ahaṃkāra the rest of the manifest world unfolds. The Sāṃkhya position on buddhi is precise: it is not consciousness. It belongs entirely to prakṛti, the changing phenomenal field. Puruṣa simply witnesses. Bondage, in this analysis, is the misidentification of the witness with what it witnesses — above all with buddhi, the subtlest and most convincing of the phenomenal functions. Liberation ([kaivalya](lexicon:kaivalya)) is the recognition that buddhi — all its judging and discerning — is prakṛti, not the witness. The instrument of that recognition is [viveka](lexicon:viveka) itself: clear discrimination, which is what a purified buddhi does.
Buddhi in the Bhagavad Gītā
The [Bhagavad Gītā](lexicon:bhagavad-gita) treats buddhi as the seat of right action. Kṛṣṇa's teaching of buddhi-yoga — acting with discernment and without attachment to results — runs through the early chapters of the text. In Chapter 18, Kṛṣṇa identifies three grades of buddhi corresponding to the three [guṇas](lexicon:gunas): a sāttvika buddhi sees dharma and adharma clearly; a rājasika buddhi confuses the two; a tāmasika buddhi inverts them. The practitioner who acts from a clear buddhi is described in Chapter 2 as sthitaprajña — one of steady wisdom, not agitated by the senses or clouded by the moods of rajas and tamas. The Gītā does not fully resolve the tension between Sāṃkhya's dualist account of buddhi as a prakṛti function and the Vedāntic view in which the same faculty belongs to the subtle body of an individual [ātman](lexicon:atman). Both framings appear in the text, and the question remains a point of scholarly discussion.
Where to encounter it in the index
Buddhi surfaces wherever the Sāṃkhya-Yoga map of the psyche is in play. Sadhguru's *Inner Engineering* delivers the yogic curriculum in which the distinction between the discriminating faculty and the witness is central to practice. Paramahansa Yogananda's *Autobiography of a Yogi* carries the kriyā yoga tradition downstream from the same Sāṃkhya-Yoga inheritance, describing the mental operations the practice is designed to refine. Rupert Spira's *Being Aware of Being Aware* approaches from a non-dual Vedāntic direction: the same question buddhi analysis asks — what is the I that knows? — is the entry point to his inquiry. Nisargadatta Maharaj's *I Am That* is the most direct contemporary treatment of what happens when the discriminating faculty turns back on itself and looks for the one who is doing the discriminating.
