"All that is necessary for the triumph of evil is that good men do nothing." 
-Edmund Burke

“It is not good for all our wishes to be filled; through sickness we recognize the value of health; through evil, the value of good; through hunger, the value of food; through exertion, the value of rest.” 

-Greek Proverb

“If you want to realize the truth, don’t be for or against. The struggle between good and evil is the primal disease of the mind.”
-Seng Ts’an

"Our life is shaped by our mind; we become what we think. Suffering follows an evil thought as the wheels of a cart follow the oxen that draws it. Our life is shaped by our mind; we become what we think. Joy follows a pure thought like a shadow that never leaves."

-Buddha

"It is man's own mind, not his enemy or foe, that lures him to evil ways."
-Buddha