Last July 25, David Barash, a professor of psychology at the University of Washington, said in a column that he had some bad news for “those opposed to abortion rights or to stem-cell studies.” These opponents take it as obvious that human life begins at the moment of conception, and hence to destroy the product of conception is to take an innocent human life. The bad news? “There is no moment of conception.”

Barash attempts to prove this “bad news” by a detailed scientific description of the process of conception, throughout which he challenges his reader to identify the precise moment when a person has come into existence. The first stage is the production of an egg (oogenesis) and of a sperm (spermatogenesis) which are destined to meet one another. “Is that moment now?” asks Barash.

I myself have never heard of anyone who thinks that a sperm cell in the body of the father-to-be and an egg cell in the body of the mother-to-be already constitute a person. Apparently Barash thinks this is a matter of some difficulty.

However that may be, the next stage is when the sperm actually touches the egg and its head binds to the egg’s zona pellucida (extracellular matrix).

“Maybe now?” asks Barash.

Next, the sperm penetrates the zona and comes up against the egg’s plasma membrane.

“Or now?”

Then, there is a kind of fusion of the sperm’s membrane with the egg’s membrane.

“Now?”

Next the egg’s membrane is depolarized, preventing other sperm from entering.

“Now?”

Soon after, more long-lasting changes take place in the egg’s zona, blocking out other sperm.

“Now?”

Then, the egg begins to pull the sperm into itself.

“Now?”

The fusion of the genetic material in each of the gametes has not yet taken place, and even after the sperm has penetrated the egg it can be a matter of some hours, often more than 24 hours, before this happens. And when this happens, it too is a gradual process.

Barash’s conclusion: “There is, to repeat, no cymbal-crashing ‘moment’ of fertilization. Natura non facit saltum [Nature does not make leaps].”

The moral: “Natural boundaries won’t ease our moral quandaries. When we most want them, they aren’t there. ... We had better give up trying to find such boundaries.”

It is certainly hopeless to take issue with Barash on the grounds that his science is faulty.

And yet this does not in the least destroy our certainty that instantaneous and sudden events do take place in nature. For instance, the beginning or end of any change is instantaneous, just as the beginning or end of a line has no length. So there are definite instantaneous markers in the externally visible processes.

Barash is apparently aware of this — so he points to a further difficulty: Which of these milestones marks the moment of the infusion of a human soul? Is it now? Or now? Or now?

He presumes we are at a loss to say which. But some of the “nows” with which he bullies us would seem to pose no difficulty for pro-life scientists or philosophers. For example, after as many as five of his “nows” (they total about seven), the sperm itself is not yet transported into the cytoplasm of the egg.

Few or no biologists would maintain that the sperm and egg, before the sperm and its genetic material have even penetrated to the interior of the egg, constitute a single biological entity or organism that has its own intrinsic drive to develop. And I doubt very much that many pro-lifers would feel compelled to say so, either. It seems much more accurate to describe this stage as the sperm and egg endeavoring to unite, rather than the first moment of their being one thing.

Hence there are really fewer “nows” than Barash would have us think that are serious candidates for the moment at which one begins to have a new single organism or totipotential cell.

Even if the Barash’s presumption were correct, though, his conclusion would go far beyond his evidence. That is, even if his opponents were thoroughly baffled, and did not seem to prefer any one “now” over any other, it would not follow that “there is no moment of conception,” but only that we might be unable to pinpoint this moment to the nearest thousandth of a second by some obvious external sign.

Barash at best presents evidence that it is difficult for us to find an unambiguous sign of exactly when sperm and egg cease to be two distinct cells or (if this is a separate and later event) when there results from their materials a single natural thing with its own tendencies. He presents not a scrap of evidence for saying that this event does not take place, or for saying that it is not decisive and instantaneous.

That essentially invisible and instantaneous changes do take place in the natural world, and that they are not readily pinpointed in time, is not really a matter of dispute. Example: Are you sensitive to temperature today? Do you feel, by your sense of touch, the differences between hot and cold? Surely. Did you have that sensitivity 500 years ago? No, you did not even exist.

Then that sensitivity must have begun to exist somewhere in time.

More than this, that beginning must have been instantaneous: There is no such thing as being “almost sensitive to temperature.” Either you are, or you are not: If you become more sensitive to temperature over time, there must still be a distinct instant before which you had no such sensitivity whatever, and after which you had some (however meager) sensitivity.

The same can be said of your ability to see, or to find something funny, or draw an inference, or deliberate about which of two things you ought to do. Nonetheless, if one looks at the genesis of the organic basis for one’s ability to do any of these things, or if one looks at such a genesis the way a biologist would (or the way Barash would), one will not see any externally obvious event signaling that “now” is the moment of the instantaneous change in question. That the change must take place and be instantaneous is certain, from the above reflection — exactly when it takes place to the nearest nanosecond is very difficult, and perhaps impossible even in principle, to determine.

Here Barash might say “Concedo: I have not really proven that there is no moment of conception. You got me. But you yourself have just admitted that we cannot pinpoint the moment, we cannot know it or recognize it with certainty and precision, and therefore we have no sure basis upon which to forbid abortions or embryonic stem-cell research.”

Well, I confess I am puzzled as to why ignorance about whether X is a human being at this exact instant entails, by default, the moral judgment, “We can do whatever we please with it.”

One would think that just the opposite was the case. I am in the woods, hunting. I catch a glimpse of a figure darting into a bush — it might have been a person, or a bear, I am not sure. Since I am not sure, I should feel free to shoot first and ask questions later, if I bother to ask at all. Is this sound moral reasoning?

Not only should we never seek, whether as an end or as a means, to destroy what we know to be innocent human life, but we should not destroy what might be a human life, for all we know.

Barash’s article reminds me of the kinds of morally dishonest questions we sometimes hear. Boys sometimes want to know what they can and cannot do with a girl before marriage. Can they do X? What about Y or Z? Is it okay to kiss? For how long? Where? How? etc.

The spirit behind the questions is, “What can I get away with?” That is to say, given that I wish to satisfy my desires as much as possible, I will put you, the moralist, in the awkward position of laying down definite and detailed guidelines, and then you will have to prove to me that X is truly an objective and instantaneous cut-off between the chaste and the lustful.

The truth is, as soon as one is genuinely interested in being temperate, one tends to err on the side of caution. One no longer seeks the scientifically exact cut-offs up to which I can “get away with it.”

Michael Augros is a professor of philosophy at the Legionaries of Christ Center for

Higher Studies in Thornwood, New York.