All forms of good also require evil.

from The Hero with a Thousand Faces by Joseph Campbell page 325 nonfiction ~1 min read

The hero of yesterday becomes the tyrant of tomorrow, unless he crucifies himself today.

From the point of view of the present there is such a recklessness in this deliverance of the future that it appears to be nihilistic. The words of Krishna, the world savior, to the wives of the dead Kans carry a frightening overtone; so do the words of Jesus: "I came not to send peace, but a sword. For I am come to set a man at variance against his father, and the daughter against her mother, and the daughter-in-law against her mother-in-law. And a man's foes shall be they of his own household. He that loveth father or mother more than me is not worthy of me: and he that loveth son or daughter more than me is not worthy of me." To protect the unprepared, mythology veils such ultimate revelations under half-obscuring guises, while yet insisting on the gradually instructive form. The savior figure who eliminates the tyrant father and then himself assumes the crown is (like Oedipus) stepping into his sire's stead. To soften the harsh patricide, the legend represents the father as some cruel uncle or usurping Nimrod. Nevertheless, the half-hidden fact remains. Once it is glimpsed, the entire spectacle buckles: the son slays the father, but the son and the father are one. The enigmatical figures dissolve back into the primal chaos. This is the wisdom of the end (and rebeginning) of the world.

—Joseph Campbell, The Hero with a Thousand Faces, p. 325