How does the source material explain the ultimate state of oneness and its connection to the feeling of supreme devotion?

The state of oneness, as described in Chapter 4, is achieved by discarding the feeling of duality and fully realizing that everything in the universe, both moving and unmoving, is Brahman by nature. This is the recognition that the glory of the universe is our own eternal majesty. The text posits that when a person fully realizes the truth of 'I am everything' in relation to the entire world, they experience an unparalleled happiness. This profound realization and the immense joy it brings is what constitutes the attainment of supreme devotion.