Between pain and pleasure, there is indifference (no
pain-no pleasure); and between two thoughts or sounds,
there is the deathless. With thin slicing of time, in each moment
that unfolds, you must see death and the deathless
in their interdependence. Where qualitative discernment is
present, our consciousness creates duality - the subject and
the object, the good and the bad and pleasure and pain.
The oscillation continues. Nibbāna is non-duality, the space
(ākāsa) between matter (rupa), the gap between pleasure
and pain (avedaitha sukha); sign-less state of perception (animitta
saññā), non-descriptive consciousness (anidassana
viññāna) or the uncreated, a state of equanimity towards all
formations (sankhāra upekkhā).
http://www.nissarana.lk/pdf/Books/Eng/VenUD_Eng_Bhaddekarrata.pdf
