Raymond Dennehy, professor of philosophy at the University of San Francisco, responds to some of the key ideas of Princeton professor Peter Singer's book The Moral Status of the Embryo.

The Logic of Death: No ‘Right’to Life

Professor Peter Singer: Once we free ourselves from a world view depending on some specifically religious premises, the early embryo has no intrinsic value and does not have a right to life. It may therefore be used, with the consent of those from whose egg and sperm it has been formed, for scientific research.

There is, of course, a standing argument against this view. The argument goes like this:

1. Every human being has a right to life.

2. A human embryo is a human being

3. Therefore the human embryo has a right to life.

To which the standard response is to accept the first premise — that all human beings have a right to life — but to deny the second premise, that the human embryo is a human being. This standard response, however, runs into difficulties, because the embryo is clearly a being, of some sort, and it can't possibly be of any other species than homo sapiens, so it seems to follow that it must be a human being. Attempts to say that it only becomes a human being at viability, or at birth, are not entirely convincing.

So the standard argument for attributing a right to life to the embryo can withstand the standard response. What the argument cannot withstand, however, is a more critical examination of its first premise: the premise that every human being has a right to life.

What is our particular objection to killing human beings, over and above any objections we may have to killing other living beings, such as pigs and cows and dogs and cats, and even trees and lettuces?

The obvious answer is that human beings are different from other animals, and the greater seriousness of killing them is a result of those differences. To take the most extreme of the differences between living things, consider a person who is enjoying life, is part of a network of relationships with other people, is looking forward to what tomorrow may bring, and freely choosing the course her or his life will take for the years to come.

Now think about a lettuce, which, we can safely assume, knows and feels nothing at all. One would have to be quite sad, or morally blind, or warped, not to see that killing the person is far more serious than killing the lettuce.

If this is the sense of the first premise, that every human being has a right to life, then what of the second premise — that a human embryo is a human being? It is immediately clear that in the sense of the term “human being” which is required to make the first premise acceptable, the second premise is false. The embryo, especially the early embryo, is obviously not a being with the mental qualities which generally distinguish members of our species from members of other species. The early embryo has no brain, no nervous system. It is reasonable to assume that, so far as its mental life goes, it has no more awareness than a lettuce.

If the first premise is true when “human” means “a being with certain mental qualities” and the second premise is true when “human” means “member of the species homo sapiens,” the argument is based on a slide between the two meanings, and is invalid.

The Logic of Life: Kind vs. Degree

Professor Dennehy: What Singer does here is to mistake a difference in degree for a difference in kind — because he misunderstands what the essence of a human being is.

A triangle is properly defined as “a figure formed by three lines intersecting by twos in three points, and so forming three angles.” No figure that lacks that essential structure is a triangle. Similarly, if the essence of a human being were “thinking or self-aware human being,” then it would, indeed, follow that any human being that lacked the capacity to think or be self-aware would not be a human being. But, although mental states, like thinking and self-awareness, are parts of our most important faculty, rationality, they are a power of our human nature; they do not constitute our essence. Just because all of a human being's faculties have not yet developed, it does not follow that it is not a human being. Rather, it is just because it is actually a human being that it will develop faculties of rationality and self-awareness.

Stage of development — like race and skin color, economic and social status, and health — is an accidental, not a substantial attribute. So, just as it is as much an act of murder to kill a black man as a white man; a poor man as a rich man; a sickly man as a healthy man, so it is as much an act of murder to kill a human being at its earliest stages of development as at its mature stage. In his attempts to defeat the standard argument against abortion, Singer wants to show that the difference between a thinking, self-aware being is one of kind, when, in fact, it is merely one of degree.

But this is common where one group of people wishes to oppress or destroy another group of people. One must kill them with words in order to justify killing them in deed. Hitler would have the world believe that the Jews were no higher on the scale than monkeys, the U.S. Supreme Court ruled that blacks were only three-fifth persons under the Constitution, and now pro-abortionists would have us believe that the unborn are not human beings or persons — not, at least, in the sense that counts.

Singer has a flare for making distinctions between humans that can justifiably be killed and those that can't. Consider, for example, the distinction he and his co-author, Helga Kuhse, make in their book, Should the Baby Live? In its preface, they offer the bald proposal, “We think that some infants with severe disabilities should be killed.” Does this mean that some adults with severe disabilities should be killed also? No. Why not? Because, Singer and Kuhse assure us, “… it is one thing to say, before a life has properly begun, that such a life should not be lived; it is quite different to say that, once a life is being lived, we need not do our best to improve it. We are sometimes prepared to say the former; we are never prepared to say the latter.”

Now, how's that for a distinction for determining who should be killed and who shouldn't: “before a life has properly begun” vs. “a life [that] is being lived”? The word “properly” is the kicker here. What does it mean? Who decides when a life has “properly” begun?

The Logic of Death: A Potential Being

Professor Singer: At this point in the discussion, those who wish to defend the embryo's right to life often switch ground. We should not, they say, base our views on the status of the embryo on the mental qualities it actually has while an embryo; we must, rather, consider what it has the potential to become.

Indeed, we do need to consider the moral relevance of the embryo's potential. But this argument is not as easy to grasp as it may appear. If we attempt to set it out in an argument of standard form, as we did with the previous argument, we get:

1. Every potential human being has a right to life.

2. The embryo is a potential human being.

3. Therefore the embryo has a right to life.

But there is no general rule that a potential X has the rights of an X. If there were, Prince Charles, who is a potential King of England, would now have the rights of a King of England. But he does not.

In short, the destruction of the embryo is wrong because it means that a person who might have existed will now not exist; and since we value people, the destruction of the embryo has caused us to lose something of value.

But this variation is faulty because it proves too much. After all, couples who use contraceptives or simply abstain from sexual intercourse also prevent the existence of people who might have existed. Since these unconceived humans are potential human beings, what's the moral difference between birth control and aborting a potential person?

The Logic of Life: A Being with Potential

Professor Dennehy: Here Singer commits the fallacy of equivocation — he uses a word as if it had the same meaning in both instances when, in fact, it has a different meaning in each instance.

The human embryo is not a potential human being, but an actual human being some of whose faculties have yet to develop. Because of what the human embryo actually is by nature, it has certain natural potentials. Look at it this way: I've never been on a pair of skis in my life. But because I'm a two-legged creature, I have the potential to ski. A snake, on the other hand, because of what it naturally and actually is, does not have the potential to ski.

When used to refer to as yet unconceived human beings, the word “potential” is a synonym for “probable.”

An engineer who proposes a new highway design might say, “This design will reduce accidents.” Nobody would dream of replying (at least not before happy hour), “Which accidents, exactly, will it prevent?” For what the engineer means is that the new design will reduce the probability of accidents. And that's just what periodic abstinence does: It prevents conception by reducing or eliminating its probability. Who would say: “When you abstained from sexual intercourse, exactly which human beings did you prevent from being conceived?” (Contraception, of course, is a different matter because it touches on the nature of the sex act — whereas, in abstinence, there is no sex act.)

Singer sees no moral difference between destroying an embryo that has been fertilized in a petri dish and destroying a sperm and an egg in a dish. If it's not wrong to destroy the former, it can't be wrong to destroy the latter, and no one would say that destroying sperm and egg is equivalent to killing a human being.

Borrowing a phrase, Singer rhapsodizes: If it is cake we want, it doesn't make much difference whether we throw away the ingredients separately, or after they are mixed together.

But no one in his or her right mind takes Singer's attempted comparison seriously. A sperm is part of the male's body, having the same chromosomal structure as every other cell in that body; an egg is part of the female body, having the same chromosomal structure as every other cell in that body. But when sperm and egg unite, they are transmuted, producing a unique being with its own genetic structure. That is why the moral difference between abstinence and abortion is not a good comparison. The one merely prevents the possibility of human life; the other destroys an actually existing human being.

Watson and Crick won a Nobel Prize for showing how the DNA code works. One thing we learned from this was that, from the moment of conception, no constituent part is added; everything unfolds according to the morphological process dictated by the DNA code.

Now, if nothing is added from conception on, answer me this: If the fetus is not a human being and a person at one moment, how does it become a human being and a person at another moment? Do you get the feeling that, if the evidence showed that embryos were self-aware and could think and choose, some people would argue that hankering after a ham-on-rye is the criterion for deciding which humans can justifiably be killed?

Raymond Dennehy is the author of Confessions of an Aging Anti-abortionist which is seeking a publisher.