Buddhi makes its first scriptural appearance in the Katha Upanishad ( I, 3 ), where it is compared in a famous simile to the driver of a horse and carriage.

: See also the chariot allegory in the Indian work Katha Upanishad, and another in the story of Vajira.

Philosophical texts from this era such as the Katha Upanishad, Shvetashvatara Upanishad and Bhagavad Gita have clear references to Samkhyan terminology and concepts.

Katha Upanishad conceives the purusha as an individual soul which Ātman ( Self ) inhabits.

In 1840 Debendranath published a Bangla translation of Katha Upanishad.

A famous verse from the Katha Upanishad states:

* The Katha Upanishad, Upanishad belonging to the Yajur Veda, in 2005.

* Katha Upanishad

The Brihadaranyaka Upanishad explicitly states the fact that since the Rudras leaving the body – causing death – makes people cry, they are Rudras.

* The Advaya Taraka Upanishad states that the true teacher is well-versed in the Vedas, is a devotee of Vishnu, is free from envy, knows yoga and is intent upon it, and always has the nature of yoga.

Maitri Upanishad states:

The Narayana Upanishad of the Krishna Yajur Veda states that the Narayana Mantra is the crowning message of the Sama-veda.

The Brihadaranyaka Upanishad states, “ According as a man acts and according as he believes so will he be ; a man of meritorious acts will be meritorious, a man of evil deeds sinful.

This period also corresponds to the composition of the Shatapatha Brahmana, which states that the victims of a Purushamedha are supposed to be released, and the composition of the Chandogya Upanishad, which lists non-violence as a virtue.

The Chandogya Upanishad ( 3. 16 ) states that the Purushamedha is actually a metaphor for life itself, and it compares the various stages of life to the oblations that are offered.

Maitri Upanishad states: