But love and hate, he thought now, good and evil, lived side by side in the human heart, and not merely in differing proportions in one man and the next, but all good and all evil. One had merely to look for a little of either to find it all, one had merely to scratch the surface. All things had opposites close by, every decision a reason against it, every animal an animal that destroys it, the male the female, the positive the negative... Nothing could be without its opposite bound up with it. Could space exist in a building without objects that stopped it? Could energy exist without matter, or matter without energy? Matter and energy, the inert and the active, once considered opposites, were now known to be one.”

Patricia Highsmith