Your life is so improbable as almost to be impossible. Consider that about a million eggs are formed within the average woman, and about half a trillion sperm are produced in the lifetime of the average man. The odds, then, that you in particular were conceived by your particular mother and father are, on this reckoning, somewhere in the vicinity of 1 out of 500,000 trillion. But consider also that the existence of your mother and father was equally improbable, as was that of your grandparents, and so on.

The universe has some 200 billion galaxies, each with on average 200 billion stars. Each star has on average 10 to the 57th atoms. Take all of the atoms of all of the stars in all of the galaxies and put them in a very big sack. Place your initials on just one of those atoms. The odds of drawing out that particular atom with your initials on it, out of all of the atoms in the entire universe, is trillions of times greater than the probability of you coming to exist as a descendent of your particular grandparents.

None of this reasoning applies, of course, if you are essentially a pure spirit, as Descartes thought, and Plato before him. If you are a pure spirit which merely happens to inhabit a body, then you exist in virtue of your activity of thinking, and for all we know you may have been thinking from the beginning of the world, even before you inhabited your body, as Plato believed. Your existence may seem to be well nigh necessary, or at least inevitable. Most people in their egoism view their own existence in that way.

But if, as the Catholic Church teaches, you are essentially embodied, and you in your individuality are essentially tied to a particular body, constituted by particular DNA, then your existence becomes highly contingent. If for example, your parents had "waited a month," then you would never have come to exist, but at best only a brother or sister of yours.

Soldiers of fortune have liked to fight in wars because of the "feeling of being alive" which they experience after surviving a deadly battle. Others skydive for the similar reasons. People have been known to convert after barely avoiding death by disease or in an accident.

But these cases are small cheese. Even in the first wave of the Normandy invasion a soldier had a two out of three chance of remaining alive. In comparison, reflection on the improbability of your bodily existence ought to induce an existential vertigo.

This improbability looks for an interpretation. Someone with a modern "scientific" cast of mind will perhaps have been trained in such a way that he will shrug it all off. "So what? I'm a product of chance," he will say, and then carry on with his work and following his favorite sports team or television show.

Such a person simply avoids thinking about it. "Chance" is nothing, and in any case his particular personality and interior life is not "produced" but rather only occasioned by his genetic make-up. We cannot refute such a person but only cite Socrates: the unreflective life is not worth living.

The only plausible interpretation is that of "gift." Life is not a neutral thing, like an electric charge or an atomic number, but an excellent good. It is a good that we enjoy not "by accident" but in the manner of a gift. We do not exist arbitrarily, but Someone has wished life for us, as a gift given to us. "If man were merely a random product of evolution in some place on the margins of the universe," Pope Benedict stated in his Easter Vigil homily, "then his life would make no sense." Contrariwise, for his life to make sense, it needs to be viewed as a gift.

I remember a conversation during lunch recess in junior high school about the meaning of life. Somehow my friends and I changed from talking about particular concerns, such as the math test that was coming up, to considering the purpose of our life as a whole. "What if life itself is a kind of test," someone one said, "and God gives you a good or bad 'grade' based on how you do?" We paused and took this very seriously. The suggestion seemed deep and philosophical to us, and very possibly true -- in which case, we wondered, how does someone do well on this "test"?

It's natural for school children, whose life consists of studies and tests, to view life itself as a big test. The example shows that we naturally look for some fundamental image or comparison for making sense of everything. Is life a test, or a struggle, like climbing a mountain, or a battle? Is it like vacation or (as I once heard in a Protestant sermon) similar to a trip over a scenic railway in an observation car?

Pope Benedict's frequent references to "the logic of gift" articulates the best image. The logic of life -- the secret which unlocks its meaning and illuminates everything else -- is that life is fundamentally a gift from the good heart of the Father, which we are meant to render back to Him: "man finds himself only through sincere gift of himself."

Our guide in doing so is the Son, since the image which most fundamentally illuminates life is The Image.

Michael Pakaluk is Professor of Philosophy at Ave Maria University and the author, most recently, of "Accounting Ethics" (Allen David Press).