Can we? Well, I say that we can, and that it is something we each need to understand. As Andrew Bernstein says in his recent examination of evil, "it is crucially important to understand the nature of evil. Evil must be examined – as an act of self-preservation – to keep it from poisoning one’s soul with the slightest bit of pessimistic despair. In the face of evil run rampant, it is crucially important to protect [what Ayn Rand called] the benevolent universe premise."
But first, let's clear up something about the nature of evil. The religionists' monopoly on morality has confused many, many things about the subject, and one them of them is this very question: whether and how evil exists. Despite what many christians will tell you, 'evil' is not some supernatural 'Satanic' force that's out there in the world, any more than God's goodness or Wotans' power or Alberich's evil curse are some sort of force in the universe.
Fairy stories like these can help illustrate morality, but we shouldn't let them form our morality for us. Rational morality -- an examination of what's good and what's not -- does not pertain to and nor is it derived from the supernatural. Morality pertains to life here on earth. Good and evil reside in the actions of individuals who perpetrate good or evil acts.
Good (as I argued at length in a recent post) pertains to those actions and to those moral principles that when acted upon lead to the advancement, the furthering, or the flourishing of human life on earth. Life is the standard which lies at the heart of a rational morality -- individual, human life. According to this principle, all that which supports or promotes an individual’s life is good, and all that retards or destroys man's life is not good.
But 'not good' is not yet 'evil.' Evil is something much, much worse. Evil isn't just the mistaken, the error-ridden, the minor stuff-up -- that's just bad. Evil is a passionate dedication to destruction; a concerted commitment to the anti-life; a deliberate defiance of facts and reason and human values: a spitting in the face of existence.
Objectivists argue that the good requires a commitment to facts, to rationality, to productiveness. Evil men stand opposed to this: opposed to reality, to the rational, to every value on which human life depends. "The principle is clear," says Andrew Bernstein, "irrationality is self-destructive... Because of this, evil is metaphysically impotent: it cannot build, grow, create, or produce. Achievements require commitment to the laws and facts of reality. Evil requires the opposite."
But this poses an obvious question: If evil men cannot even sustain their own lives, how do they acquire the power to destroy? Andrew Bernstein answers this and much more in his superb five-part examination of Villainy: An Examination of the Nature of Evil -- including a controversial argument: that it is most moralists who are most responsible for most of the evil in the world.
I highly recommend it.