People normally cut reality into compartments, and so are unable to see the interdependence of all phenomena. To see one in all and all in one is to break through the great barrier which narrows one's perception of reality.
Various, Ledi Sayadaw, Bhikkhu Khantipalo, Nyanaponika Thera, Padmasiri de Silva (2012). “Collected Wheel Publications Volume XVI: Numbers 231–247”, p.90, Buddhist Publication Society