Generally, in the Upaniṣads the Supreme Absolute Truth is described in an impersonal way, but the personal aspect of the Absolute Truth is mentioned in the Īśopaniṣad, where we find the following verse:
- hiraṇmayena pātreṇa satyasyāpihitaṁ mukham
- tat tvaṁ pūṣann apāvṛṇu satya-dharmāya dṛṣṭaye
"O my Lord, sustainer of all that lives, Your real face is covered by Your dazzling effulgence. Kindly remove that covering and exhibit Yourself to Your pure devotee." (Śrī Īśopaniṣad 15) The impersonalists do not have the power to go beyond the effulgence of God and arrive at the Personality of Godhead, from whom this effulgence is emanating. The Īśopaniṣad is a hymn to that Personality of Godhead. It is not that the impersonal Brahman is denied; it is also described, but that Brahman is revealed to be the glaring effulgence of the body of Lord Kṛṣṇa. And in the Caitanya-caritāmṛta we learn that Lord Caitanya is Kṛṣṇa Himself. In other words, Śrī Kṛṣṇa Caitanya is the basis of the impersonal Brahman.