Sri Aurobindo translates Mundaka Upanishad, Chapter 3, Section 1, Verse 7: “Vast is That, divine, its form unthinkable; it shines out subtler than the subtle: (Or, ‘minuter than the minute:’.) very far and farther than farness, it is here close to us, for those who have vision it is even here in this world; it is here, hidden in the secret heart.”
The Upanishadic sages wrestled with a conundrum. They had to figure out how to define what they knew to be beyond all definitions, to describe what they knew to be indescribable. They were concerned that whatever form or definition they provided would be simply a limitation that would turn that “truth” into an “untruth”. They knew however that somehow the mind of the seeker needed to be attuned to the divine Truth, and thus, some method must be found. They recognized the need for both a “negative” and a “positive” affirmation. The negative took the form of saying things like “neti, neti”, “not this, not that” to ensure that the Absolute would not be artificially limited in any specific form. At the same time, they recognized that there was a need to provide a positive statement about what the Absolute is. The present verse is an attempt, therefore, to describe, in positive terms, the Absolute.
The Rishi starts with an image of the universe in its unimaginable vastness, impossible for the human mind to truly grasp, beyond all capabilities of human senses. Brihat, vast is one of the three terms linked together by the Upanishads when they attempt to put terminology to the Absolute (Satyam, Ritam, Brihat, the Truth, the Right, the Vast). To ensure that the seeker does not get lost in this vastness, the Rishi then points out the subtlety, and further, it is both far and near, it is here in this world within which we live, and is hidden in the secret heart.
The purpose here is not to set forth a series of logical points of definition but to “texture the awareness” to see the divine Presence in everything without exception, including both those things within our sight and grasp, and those that go beyond our perceptions. For the awakened seer, for the eye that sees, the divine Presence permeates all existence, and transcends all at the same time. This is not a statement of limitation of the divine, but a recognition of the limitations of our mental consciousness. When we think we have defined it, we have failed to capture it in its entirety. When we seek it through renunciation, to achieve oneness with the Absolute, we may be missing it right here in the world of forms and in our own heart. This is what Sri Aurobindo calls “reality omnipresent”. All of the paradoxical statements are meant to define, and yet not limit, the Absolute.
Sri Aurobindo, The Upanishads, Mundaka Upanishad, pp. 193-210