Do you remember the birth of your first child, your wedding day, the day you got engaged? Of course you do. Now look back: remember college, high school, the prom and the playground, confirmation and first Communion. Go all the way back, to your first memory of sitting in the playpen or being a toddler on your mother's knee — or, more likely, a toddler cannonballing into your mother's knee (let's be real here).

What do you find about yourself, all this time? You're the same you — just like the newspaper that you're reading is the same newspaper, and the chair you're sitting on at the table as you read is the same chair, at the same table, from moment to moment. The world we live in is not one that operates on radical, arbitrary changes in what something is.

Or is it?

The World We Live In

Today, natural science, philosophy and religion all seem to allow for a universe full of unexplained, dramatic change — consider the astounding leaps that supplement most modernizations of Darwin's theory or the reinventions of God, person and things according to human use and understanding.

Likewise, when it comes to human life and personhood, modern man is willing to accept strange notions of sudden changes before he'll accept a straightforward explanation. For instance, the nonsectarian Hastings Center for bioethics defines life as “the state of being self-aware, capable of rational thought and of moral agency.”

Really? Think about it. You have not always been self-aware and at times been only potentially rational or moral. Yet you've always been you.

How do you know you've always been you?

It seems a simple question, and Aristotle and St. Thomas Aquinas gave it a simple answer. They said you can consider yourself a substance. According to this way of thinking, the form of you body — the form of your body is your soul, by the way — informs the matter that makes up your body. It keeps everything together in one package and in order as it slowly and imperceptibly develops from day to day. This starts as soon as everything is there and working at all (with modern tools of observation, obviously conception) until it stops (clinical death, at the very earliest).

Not everyone accepts this theory of substance. And even if they did, the early history of the substance that is you might still puzzle Aristotle himself. Let's think about this for a moment.

A human chromosome was first mapped in December 2000. Now, after intensive efforts, a complete mapping of a human genome is expected by the end of 2003.

And, from the moment of conception, the new single-celled human life that was you was governed by just such a unique, individual genome — in fact, it was this genome that distinguishes the new life form “you” as human. And this genome — one could almost think of it as a map of the you, the life form — has remained and will remain the same throughout your entire life, right on until death.

More likely than not, at least one person out there reading this is thinking: “But what about me and my twin?” — of course, an identical twin. Identical twins share the same genome — but not the same form. Like two travelers using the same map, their ways are at once identical and distinct.

Once the map is in place, it's a question of development. Each ability, each function, each organ, develops apace in its own appointed time. By the 14th day, the newly implanted life form — called, at that stage, a blastocyst — is sending hormonal signals back to the mother. At that same point, we see the development of the so-called “primitive streak” — the precursor of the brain and nervous system, which will assume many of the functions regulated by the genome itself in the first days and weeks of life.

You are the same you who was in high school, in nursery school, in diapers, in the cradle… and in the womb.

And just as the genome is not itself the form but the most immediate map or physical manifestation of form accessible, so too is any organ — whether eyes or ears, brain or central nervous system — a physical manifestation of the function it represents.

What of the soul? When does that come into play? In the case of our own kind, the process I've described forms a unique, precious, unrepeatable human person, known by faith to be destined for eternity. But you don't need to understand the soul to grasp this point.

Human Life, Human Soul

Bioethics is philosophy. And good philosophy will recognize that what is there at the beginning develops and becomes what is there at the end, and it remains the same thing from beginning to end. Yet why do so many treat bioethics as science, religion or both?

The key problem here is where the modern world tends to look for truth. It looks to science for truth about matter and to religion for truth about spiritual things. But, as it happens, revealed religion is about a very limited set of truths, and natural science is not about truth at all.

Wait a minute — natural science isn't about truth? Well, it isn't.

It's about making observations, conducting experiments and then organizing, categorizing and quantifying data into hypotheses or theories to explain what has been observed. These theories can always be improved — either by concocting something that better fits the observations you've made or by using new tools or methods to make better observations. Thus, the great philosopher of science, Sir Karl Popper, wrote that no scientific theory can ever be proven; it can only withstand falsification — that is, avoid being disproven. Indeed, that's why science keeps improving; it's built into the mechanism.

But, by the same token, scientific results are always tentative — sort of an interim report card on a term that never ends.

And wait another minute: How come religion teaches about very few truths — what about the Church's position on abortion, contraception, euthanasia and so on? These determinations are the magisterium's equivalent of case law.

Remember The Paper Chase? John Houseman says, “Could someone please recall for me the details of Hockenheim v. Superior Laundry — Mr. Hart,” and Mr. Hart struggles like a butterfly on a pin, explaining how the details of the specific case reflect the broader character of the civil law.

Everything the Church says about the hot-button issues is nothing but specific application of its views on human dignity and the nature of the human person — two of the relatively few subjects the Church addresses extensively.

The Church's interest here, as everywhere, is well beyond the scope of bioethics — indeed, it exceeds the bounds of life itself as we know it.

As John Paul II writes in his 1995 encyclical Evangelium Vitae (The Gospel of Life):

“Life in time, in fact, is the fundamental condition, the initial stage and an integral part of the entire unified process of human existence. It is a process which, unexpectedly and undeservedly, is enlightened by the promise and renewed by the gift of divine life, which will reach its full realization in eternity.”

Former Register associate editor Paul Chu writes from New Haven, Connecticut.