That is Brahman. That is the Ātman. Its members are the other deities.

This brief but profound anuvāka synthesizes the essential teaching of the Upaniṣad: Mahaḥ (the fourth Vyāhṛti) is Brahman and is the Ātman. The three previous Vyāhṛtis (Bhūḥ, Bhuvaḥ, Suvaḥ) together with the worlds, the devas, the Vedas, and the prāṇas are its members — dependent upon It as the arms and legs depend upon the body.

This is the saguṇa (with attributes) manifestation of Brahman, often identified with Hiraṇyagarbha, the Cosmic Being who animates the entire universe. It is the Sūtrātman, the Thread that runs through and unites all of creation.

For the practitioner, this means that all deities and all aspects of the universe are but extensions of the One Brahman-Ātman. In meditation, we can contemplate any form — whether Agni, Vāyu, or the sun — as a “doorway” toward the supreme reality, always remembering that these forms are members, not the complete body; they are symbols, not the ultimate Reality.

The contemplation of Brahman through symbols is valid and useful, but must culminate in the understanding that Nirguṇa Brahman (without attributes), the pure Ātman, is the final truth.