If optimism means a general approval, it is certainly true that the more a man becomes an optimist the more he becomes a melancholy man. If he manages to praise everything, his praise will develop an alarming resemblance to a polite boredom. He will say that the marsh is as good as the garden; he will mean that the garden is as dull as the marsh. He may force himself to say that emptiness is good, but he will hardly prevent himself from asking what is the good of such good. This optimism does exist — this optimism which is more hopeless than pessimism — this optimism which is the very heart of hell.
Against such an aching vacuum of joyless approval there is only one antidote — a sudden and pugnacious belief in positive evil. This world can be made beautiful again by beholding it as a battlefield. When we have defined and isolated the evil thing, the colours come back into everything else. When evil things have become evil, good things, in a blazing apocalypse, become good. There are some men who are dreary because they do not believe in God; but there are many others who are dreary because they do not believe in the devil. The grass grows green again when we believe in the devil, the roses grow red again when we believe in the devil.
— Charles Dickens (1906).