We need not fear what seem to be contradictory impulses to both help and avenge. Tension and drama are part of the human condition. Our Catholic faith can give us an explanation for these sometimes bewildering feelings, and guidance about how best to channel them.

Maybe you have felt that blinding, murderous fury at the terrorists and their allies. I have noticed that I could slide over the line that divides righteous anger from visceral rage.

Some modern thinkers would have you believe that these feelings are evidence of a xenophobia inherent in Western civilization — proof that we Westerners really are, at root, racist savages. Others might claim that these feelings stem from the outdated and irrational belief that good and evil are real. If only we could get beyond good and evil, we would not be so powerfully moved by the desire to avenge the thousands of deaths at the Twin Towers.

We could rid ourselves of these passions only by eliminating the ideas of good and evil, which are, after all, only social constructs.

Our Catholic faith offers a different theory about these feelings. A long line of Western thinkers, led by St. Paul, St. Augustine and St. Thomas Aquinas, tell us that these feelings are the result of original sin.

Because of original sin, each of us has a clouded intellect, a forgetful memory, a weakened will and a tendency to succumb to our passions. If you are like me, you sometimes find yourself not caring very much whether our stray bombs hit a hospital. We needn't write ourselves off as hopeless. If you feel anger coursing through your veins, overriding the intellect and rationality, you are feeling the effects of original sin. You are not some kind of freak. This is part of the human condition.

In this same period since Sept, 11, you have probably felt some other, more edifying feelings: the desire to help, the beauty of human solidarity, the peace that comes from moral clarity, the knowledge that happiness is found in giving. Theologians have an explanation for this too: This is evidence of the desire for God, which he places into the heart of every human being. Truth, Beauty and Love — these the among the names of God.

St. Thomas teaches that man is always drawn to the good. But, because of original sin, we are often confused about what is truly good. We mistake our passions for true goods. We mistake temporary goods for the permanent good, which is God. We kid ourselves into overlooking the negative impact of our actions on others.

We want to see ourselves as good, and we often lack the courage to face our shortcomings. But even this is evidence for St. Thomas's major premise. We insist on defining ourselves as good. We find it almost intolerably painful to see ourselves as anything other than good.

We are not really convinced by the intellectuals who pretend to be “beyond good and evil.” If good and evil were nothing but social constructs, we would not run so hard from the “evil” label. We would simply shrug when someone calls us, or our actions, wrong.

We sometimes think that we are entitled to have My Answers to All Life's Questions, a nice, neat paperback book with our byline. But this is just our spiritual immaturity talking. We know, deep down, that each of us has a desire for good, as well as a tendency toward evil. These contradictory impulses create much of the tension and drama in our lives.

This tension can actually give meaning to even the most ordinary of lives. Every person, from every walk of life, faces this battle within the self on a daily basis. Even a person with a boring job can know that the seemingly small decisions of his life have significance.

Do I succumb to my irritation over my husband's dirty socks all over the floor, and chew him out? Or do I choose to overlook the socks, and focus on the good that he does for the family? Whether we stay married or become another divorce statistic lies in the balance of thousands of such seemingly trivial decisions.

Alexander Solzhenitsyn has said that the battle line between good and evil goes right down the center of every human heart. By seeing that these tendencies are inherent in the human condition, and not evidence of some pathology, we can all participate in that great combat within ourselves.

The outcome of that interior war truly does determine what kind of world we will create, and winning the interior war is the Christian's ultimate mission in life anyhow.

Jennifer Roback Morse is a research fellow at the Hoover Institution and the author of Love & Economics: Why the Laissez-Faire Family Doesn't Work.