The existent and the non-existent form a pair. Between them is the Fire. That is the excellent scat of Udana as the Brahmanas know.
सच्चासच्चैव तद् द्वन्द्वं तयोर्मध्ये हुताशनः। एतद् रूपमुदानस्य परमं ब्राह्मणा विदुः॥