The word's field
Buddhi is formed from the root budh, to wake, to know, to be aware, and it names the faculty that wakes to a thing and settles what it is. Across the Sanskrit tradition the word covers a spread of related senses: intelligence, understanding, the power of forming and holding a determination, and the settled judgment that results. It is the faculty that decides, as distinct from the faculty that merely registers or wavers.
In the analytical psychology of the Samkhya tradition, buddhi has a fixed technical place. It is the first evolute of primordial nature, the highest of the inner instruments, and it stands above ahamkara, the sense of self, and above manas (see manas), the coordinating mind that gathers the senses. Where manas presents, buddhi determines. Its defining act is adhyavasaya, the resolve or ascertainment by which the psyche passes from presentation to decision. This ranking gives buddhi its characteristic role in the philosophical texts: it is the near neighbor of consciousness, the faculty closest to the witnessing self, and therefore the faculty whose purification or misdirection matters most.
The Upanishadic and Vedantic tradition inherits and reweights this scheme. In the imagery the commentarial tradition reads out of the Katha Upanisad, the self rides in the body as in a chariot; buddhi is the charioteer and manas the reins, so that discerning intelligence, not appetite, holds the office of steering. The word thus sits at a hinge in the tradition's map of the interior: below it lie sensation and the wavering mind, above it or beyond it lies the self that buddhi is meant to serve. Its career is the career of a governing faculty, prized when it is steady and single, distrusted when it is scattered.
In the corpus
Within the Logoi corpus the lemma buddhi appears 15 times across 4 works. The distribution is markedly uneven. The Bhagavad Gita carries 7 of those occurrences, nearly half; the Brhadaranyaka Upanisad carries 5; the Chandogya Upanisad 2; and the Katha Upanisad 1. The remaining principal Upanishads in the corpus do not register the lemma at these counts.
That shape is telling. The Gita's concentration reflects a text for which buddhi is a working term of art rather than an incidental noun: the poem develops an entire discipline named after the faculty, and returns to it to classify persons and paths. The Upanishadic occurrences are fewer and more diffuse, consistent with texts that treat the discriminating intellect as one station in a larger anatomy of the self rather than as the organizing concept of a practice. The single Katha attestation is slight in number but heavy in influence, since it stands near the tradition's most cited image for what buddhi does.
Canonical moments
The Gita's second chapter establishes the term as the name of a discipline. At Bhagavad Gita 2.44 the settled, single-pointed intelligence is set against a mind scattered by desire for enjoyment and power; the resolute buddhi is the one that can be gathered into concentration, while its opposite dissipates into many branching aims. A few verses on, Bhagavad Gita 2.65 locates the fruit of a steadied intelligence in the calming of sorrow and the quick establishing of the faculty in its proper standing once the affections are quieted. Together these loci mark buddhi as the seat of steadiness that the poem's early argument works to secure.
The classification passage at the poem's close is where buddhi is most fully anatomized. At Bhagavad Gita 18.30, Bhagavad Gita 18.31, and Bhagavad Gita 18.32 the intellect is sorted into three grades: the intelligence that knows action from inaction, bondage from release, and what is to be done from what is to be feared; the intelligence that mistakes one for the other; and the intelligence wrapped in darkness that takes wrong for right and inverts every measure. Here buddhi is not a single power but a graded one, and its grade decides the moral standing of the person who acts by it.
The Upanishadic side of the record appears at Brhadaranyaka Upanisad 2.1.20, where the lemma stands within that text's account of how the manifold issues from the self, the discriminating faculty numbered among the powers that unfold from the one. The locus places buddhi inside a cosmological and psychological derivation rather than a practical discipline, which is the characteristic Upanishadic setting for the word.
A note on the surfaces: the source licenses for these editions do not permit public display of running text, so each receipt link lands on a citation-pointer page that locates the passage rather than reproducing it. The pointer fixes the locus; the reader consults an edition for the text itself.
The word's world
Buddhi is the discriminating intellect, and its nearest kin within its own tradition is manas, the coordinating mind it governs, together with citta, the broader field of mental activity in which determinations form. Above the whole apparatus of inner instruments stands atman, the self that buddhi is meant to serve rather than to be, and beyond the psychology proper lies purusa, the witnessing consciousness for whose sake, in the Samkhya account, the intellect functions at all. The discipline the Gita builds on the faculty shades toward jnana, the knowing that steadied intelligence makes possible.
Across the traditions the office of buddhi has recognizable analogues. The Buddhist canon distributes something of its work between citta, the heart-mind, and panna, the discerning wisdom that judges rightly, so that the discriminating function survives even where the metaphysics that housed buddhi is set aside. In the Greek map the governing intellect answers to the tradition of reasoned mind gathered under psyche, and in the Latin the deliberative faculty is named by mens, the mind that judges and decides. What these words share with buddhi is the post of the faculty that resolves: the power that does not merely take in the world but settles what is to be made of it, and by settling, steers.
Grounding: corpus figures and citations from the live Logoi corpus record (receipt soul-word-journey-v0). Cross-references: manas, citta, atman, purusa, jnana, panna, mens.