Oh, there is evil afoot the world, yes. And it is prominently on display in Carlos Eire's memoir , Waiting for Snow in Havana, my current reading. Minor evil, like ten-year-old Carlos and his young pals blowing up lizards with firecrackers. And major evil, like the gratuitous humiliations and tortures practiced by Batista's secret police and, subsequently, by Castro's goons and militias. And evil misconceived as good, as when John and Bobby Kennedy sent 1500 Cubans on the ill-planned Bay of Pigs invasion, letting them be slaughtered on a swamp-bound beach without the promised air cover.
Oh, yes, there is evil in the world.
Call it, if you want, original sin. Certainly a propensity towards violence, particularly by males, seems to have been part of the original human genetic bequest. Altruism, too. The good angel on the right shoulder and the bad angel on the left, whispering their encouragements. The eternal struggle we inherit from the four-billion-year dynamic of natural selection.
Eire's teachers, as did mine, personified evil. Satan. Lucifer. The Angel of Darkness. Abroad in the world with all his works and pomps, his imps and incubi and succubi and unclean spirits. Us against them.
Perfectly natural, of course. Animism appears to be the default human explanation of the world. Certainly it is for children, who instinctively draw faces on flowers and the sun, and (as per Piaget) ascribe human awareness to clouds and trees. True, also, of every people in every place, who in pre-scientific times, gave human qualities to rocks and pools, thunder storms and mountains. Good spirits roamed the world, and bad. Gods and devils proliferated. Carl Sagan's "demon-haunted world."
Perhaps the greatest discovery of empirical science is this: The emergent human concepts of good and evil, love and justice, self-respect and guilt, are part of a continuum of developing awareness that links us to all of earthly creation. Projections of ourselves onto the non-human world is natural but illusory. The dryads and naiads are a fiction. So too is Zeus and all his retinue. So too is Satan.
Which is not to say that evil isn't personified. We all manifest it to one degree or another as part of our human nature. And, blessedly, most of us, most of the time, align our wills with the angel on the right shoulder.