In the end they are taught by a king that the universal Spirit is one's own spirit (5.18.

1).
It is interesting to see that, although the Rig Veda distinctly says that 'being was born of not-being' (_asatas sad aj[=a]yata_, X.72.
3),[13] yet not-being is here derived quite as emphatically from being.

For in the philosophical explanation of the universe given in 6.2.1 ff.

one reads: "Being alone existed in the beginning, one, and without a second.

Others say 'not-being alone' ...