Many critics of my Susan Smith satire, in which I used pro-choice arguments to defend infanticide, attacked me for ignoring the real issue: namely, that the humanity of the infant overrides all the pro-choice arguments.

That omission, however, was the whole point, demonstrating that the pro-choice side often does exactly the same thing. If the human embryo or fetus is a person with the right to life, then the "choice" rhetoric I used does not apply to abortion at all, ju st as it does not apply to infanticide (though some, incredibly, seem to think it does).

This means that the real issue of abortion is not freedom from government, or personal privacy, or a woman's right to choose, or overpopulation, or quality of life, or patriarchal oppression of women, or anything except the human right to life (and that's ethics, not law). Honest and rigorous moral reasoning shows that if this right holds just after birth, then it must hold from conception. (Sources: Francis J. Beckwith, Citizen magazine, Nov. 15, 1993, and The Human Development Hoax: Time To Tell The Tr uth!, by C. Ward Kischer and Dianne N. Irving.)

First, the evidence from human embryology shows clearly that post-fertilization growth - before and after birth - is a gradual process, without clear boundaries between stages. As Kischer puts it, "Human development is a continuum in which so-called stag es overlap and blend into one another, even after birth and unto death."

This means that time restrictions on the right to life cannot be logically consistent. For instance, if you believe a woman's right to choose expires after three months, what suddenly happens at midnight on day 90? Why is the fetus fully human then, but n ot 5 minutes before? Why do all the "choice" arguments suddenly not apply?

Other efforts to defend abortion rights also fail. The viability argument defines human life in terms of the current state of technology, also failing to note that a born infant requires far more care than a pre-born one and is clearly incapable of an "in dependent existence." Similar attempts, such as "sentience," either are arbitrary (like time limits) or immediately justify infanticide (as the grimly amusing umbilical cord argument does).

The last defense of the pro-choicers is that uncertainty implies a lack of human rights. In other words, we can't decree that an organism has human rights unless we are reasonably sure it is human. But since the right to life is far more important than th e right to choose, the opposite is true. We cannot deny human rights unless we are reasonably sure the organism is not human.

When the organism is a human embryo, we are far from sure. Any medical textbook will tell you that at the moment the sperm and the egg join, a new human being, with a complete and unique genetic code, has come into existence. (In fact, its individuality a t once endangers its life, since its mother's body recognizes it as an alien, not part of the mother's tissues. It must use highly specialized structures, not yet understood, to fight its way into the uterine wall; thus, many pregnancies spontaneously abo rt without the mother's knowledge.)

There is expert testimony as well. Beckwith quotes a Mayo Clinic physician: "...it is an established fact that all life, including human life, begins at conception." A French geneticist testified before the Senate that conception as life's origin "is no l onger a matter of taste or opinion...it is plain experimental evidence."

Thus, we are far from sure, and one can therefore make a compelling case for the full humanity of the unborn child, from the moment of conception. Though a zygote looks and acts very differently from the 3-year-old it may live to become, it carries within it all the genetic information necessary to do so. (This clearly distinguishes it from, say, a sperm or a red squirrel.)

Given the casual violence so rampant today, it seems clear that we must value human life more, not less. Men and women must bear responsibility for the children they conceive, "accidentally" or not, and no one should be allowed to carry out a summary dea th sentence on an innocent life. An unwanted pregnancy can put a woman in grave circumstances, and it is understandable to want there to be a way out, to look away from the question of life and death. I did, for a long time. But the first and only issue s hould be whether the human embryo has the same rights as a newborn infant. Based on the evidence, I am convinced that it does.

John Keisling , formerly pro-choice, is a math Ph.D. candidate whose column appears Wednesdays.