The Upaniṣads are the main sources of the Vedānta philosophy which has gained a pre-eminent place, in Indian philosophy superseding the other systems.
One of the most important subjects discussed by the Upaniṣads is Brahman, the Absolute, the origin and substratum of this created universe.
Out of the several terms used in the Upaniṣads to designate Brahman the word ‘Bhūman’ or ‘Bhūmā’ is an uncommon one, used only in the Chāndogya Upaniṣad (7.23-25). Literally, it means ‘that which is very big or great’.
Nārada, the well-known sage of the purāṇas, approaches Sanatkumāra, the great teacher of his times, and begs him for instruction regarding the Ātman or the Self, the knowledge of which alone can give freedom from sorrow.
Sanatkumāra teaches him the techniques of a graded meditation, the objects chosen for the same varying from nāma or name up to prāṇa or the vital energy responsible for life. In this series Bhūmān comes last. When this Bhūman is experienced, one attains supreme joy, compared to which all the pleasures of life pale into insignificance.
This Bhūman is not only everywhere and in everything, it is also our inner Self. One who realizes this becomes ‘svarāḍ,’ ruler of his own self. He also attains the freedom to move in all the regions of this universe.
This section of the Chāndogya Upaniṣad is known as Bhūmavidyā.