Once we ate from the tree of knowing good with evil, our world became a place of compounds and mixtures.
You will not find beauty without ugliness, joy without sorrow, pleasure without pain. You cannot invent a thing that will provide benefit without threat of harm, or a man on this earth who does only good without fault.
Wherever you will find one form of good, you will find another sort of evil. And where that evil does not lie, another will take its place. Rare it is, so rare, to find pure and simple goodness in a single being.
Therefore, do not reject any thing for the harm it may render, nor despise any man for the ugliness within him. Rather, use each thing towards the purpose G‑d conceived it for, and learn from each man all he has to offer.
Based on letters and talks of the Rebbe, Rabbi M. M. Schneerson 
