‘Being’ is at the heart of Vedam
In the celebrated lines of the Katha Upanishad:
‘Not by speech, not by mind,
Not by sight is It be apprehended.
How else is It comprehended
Otherwise than as: ‘It is’ ?’
From the Chandogya Upanishad: ‘In the beginning there was ‘Being’ alone; the One without a second‘.
What later becomes the ‘Subtle Inner Essence’ of the Upanishad and improved over time, becomes the Vedanthic ‘True Self’, which again if [and only if] properly interpreted, would be identical to Shūnyam.