Can you explain the concept of non-duality as it is presented in Chapter 5 in relation to a wise person?

Chapter 5 touches upon the philosophical state of a truly wise person, explaining that their bodily activities happen according to previous karma, and they are not the 'doer' of karma. The text uses a powerful analogy to describe their state of non-duality, stating, 'Only if the sun were to enter darkness would a wise man have the sense of duality.' This implies that for a realized soul, the distinction between self and other, or self and the universe, ceases to exist. As Chapter 5 puts it, for such a person 'whose own form is the entire universe, he resides in non-duality.'