Within the infant rind of this small flowerPoison hath residence and medicine power.For this, being smelt, with that part cheers each part;Being tasted, stays all senses with the heart.Two such opposèd kings encamp them still,In man as well as herbs—grace and rude will. And where the worser is predominant,Full soon the canker death eats up that plant.(Inside the little rind of this weak flower, there is both poison and powerful medicine. If you smell it, you feel good all over your body. But if you taste it, you die. There are two opposite elements in everything, in men as well as in herbs—good and evil. When evil is dominant, death soon kills the body like cancer.) 
William Shakespeare
good-and-evil, opposite-elements