Somewhere in the first millennium BCE, in forest hermitages and royal courts across northern India, teachers and students began asking questions that the fire ritual could not answer. What is it that sees through the eyes and hears through the ears? What remains when the body falls away? Is there one thing, knowing which, everything is known? The conversations that followed were remembered, polished and eventually gathered into the texts we call the Upanishads.
They sit at the end of each Veda, and so they are called Vedanta, "the end of the Veda", in both senses: its final section and its final purpose. For many Hindus they are the heart of the whole tradition.
Sitting near
The word upanishad is usually explained as upa (near), ni (down) and shad (to sit): to sit down close to a teacher. The picture is of a student at the feet of a guru, receiving a teaching too subtle to be shouted across a hall. Shankara, the great commentator of around the eighth century, offered another reading from the same root: that which loosens or destroys, because this knowledge destroys ignorance. Both are worth keeping.
Tradition counts 108 Upanishads, following a list in the Muktika Upanishad, and more exist beyond that. A smaller group is regarded as principal (mukhya), largely because Shankara wrote commentaries on them: the Isha, Kena, Katha, Prashna, Mundaka, Mandukya, Taittiriya, Aitareya, Chandogya and Brihadaranyaka. The Shvetashvatara, Kaushitaki and Maitri are often added. The Brihadaranyaka and Chandogya are the oldest and longest; the Mandukya, at twelve verses, is the shortest.
These are not systematic treatises. They are dialogues, stories, riddles, prayers and sudden flashes of insight, usually set in a human scene: a father instructing his son, a king questioning a sage, a wife asking her husband what wealth is worth if it cannot make her immortal, a boy waiting at the door of Death.
Brahman and Atman
Two words carry most of the weight. Brahman, from a root meaning to grow or expand, is the ground of all that exists: not a god among gods but the reality from which the gods, the worlds and we ourselves arise. The Taittiriya Upanishad describes it as that from which all beings are born, by which they live, and into which they return. Atman is the self: not the body, not the mind, not the personality, but the awareness that witnesses all of these. The Brihadaranyaka calls it "the unseen seer, the unheard hearer, the unthought thinker".
The central discovery of the Upanishads is that these two are not two. The reality outside and the awareness inside are the same reality. The texts approach this by negation, neti neti, "not this, not this", stripping away everything that can be made an object, and by affirmation, in short sayings that compress the whole teaching into a few syllables.
The four great sayings
Later Vedanta singled out four sentences, one from each Veda, as the mahavakyas, the great sayings. Each states the identity of Atman and Brahman from a different angle.
Prajnanam Brahma, "Consciousness is Brahman", comes from the Aitareya Upanishad of the Rig Veda. Whatever is known is known by consciousness; the Upanishad concludes that this consciousness is itself the ultimate.
Aham Brahmasmi, "I am Brahman", is from the Brihadaranyaka Upanishad of the Yajur Veda. The text says that in the beginning Brahman knew itself as "I am Brahman", and whoever realises this likewise becomes the all. It is spoken in the first person, as a realisation rather than a doctrine.
Tat Tvam Asi, "That thou art", from the Chandogya Upanishad of the Sama Veda, is a teacher's words to a student. It is the most famous of the four, and the story around it is told below.
Ayam Atma Brahma, "This self is Brahman", is from the Mandukya Upanishad of the Atharva Veda, which examines the self through waking, dream, deep sleep and a fourth state beyond them, all held in the syllable Om.
Not every school reads these sayings the same way. Shankara's Advaita takes them as plain statements of identity: the self and Brahman are one without a second. Ramanuja's Vishishtadvaita reads "That thou art" as saying that the self is a part or mode of Brahman, as a body is to its indwelling soul, distinct yet inseparable. Madhva's Dvaita holds that the self is eternally dependent on and distinct from God, and reads the passages accordingly. The sayings have carried all these conversations for a thousand years.
Uddalaka, Shvetaketu and the salt
The sixth chapter of the Chandogya Upanishad tells the story most Hindus know best. A boy named Shvetaketu, son of the sage Uddalaka Aruni, is sent away at twelve to study the Vedas. He returns at twenty-four having learned them all, and, the text says drily, thinking himself learned, proud and stiff.
His father asks him a question. Since you are so proud, did you ask for that teaching by which the unheard becomes heard, the unthought thought, the unknown known? Shvetaketu has no idea what he means. Uddalaka explains with examples. By knowing one lump of clay, everything made of clay is known; the pots and jars are only names, the clay is the reality. So too with gold and iron. Behind the many forms there is one Being, sat, from which all this has come.
Shvetaketu asks to be taught further, and his father gives a series of lessons, each ending with the same refrain. He asks the boy to fetch a fruit of the banyan tree, to break it open, and to break open the tiny seed inside. What do you see? Nothing, father. From that nothing you cannot see, says Uddalaka, this great tree grows.
Then comes the salt. Put this salt in water, Uddalaka says, and come to me in the morning. The next day he asks for the salt back, and of course the boy cannot find it; it has dissolved. Sip from the top, says the father. How does it taste? Salty. From the middle? Salty. From the bottom? Salty. The salt is not visible anywhere, yet it is present everywhere. Just so, Being is not seen, but it pervades everything, including the one who is looking for it.
That which is the subtle essence, this whole world has as its self. That is the Real. That is the Self. That thou art, Shvetaketu.
The refrain is repeated nine times in the chapter, with the rivers flowing into the sea, the dying man, the blindfolded traveller finding his way home. The repetition is itself the teaching: the truth is simple, and we need to hear it many times before we hear it.
Why this matters now
It is easy to admire the Upanishads as philosophy and miss that they are addressed to a person, usually a young one, who is confused about who they are. Shvetaketu's problem is not that he knows too little but that his learning has not touched him. The Upanishads insist that scripture is for realisation, not recitation; that a teacher is needed; and that what is sought is not far away but closer than anything else.
Where to begin reading
Start with the Isha Upanishad, eighteen verses that can be read in ten minutes and reread for a lifetime. Then the Katha, with its story of Nachiketa and his three boons from Yama, Death. Then the sixth chapter of the Chandogya, read slowly, aloud if you can. Keep a translation with the Sanskrit alongside, and when a term like atman or brahman appears, pause and ask what in your own experience it might be pointing to. Learning without that pause is what Shvetaketu came home with.