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Issue #10

Are Embryos Constructed or Do They Develop?

By Scott Klusendorf

Failure to answer this question correctly explains why so many people find pro-life views absurd.

For pro-life advocates, the case we present seems clear and to the point. From the earliest stages of development, the unborn are distinct, living, and whole human beings. True, they have yet to grow and mature, but they are whole human beings nonetheless. Embryologist Keith L. Moore writes: “A zygote is the beginning of a new human being. Human development begins at fertilization, the process during which a male gamete or sperm … unites with a female gamete or oocyte … to form a single cell called a zygote. This highly specialized, totipotent cell marks the beginning of each of us as a unique individual.”1 At the same time, there is no morally significant difference between the embryo you once were and the adult you are today that would justify killing you at that earlier stage of development. Differences of size, level of development, environment, and degree of dependency are not good reasons for saying you had no right to life then but you do now.

So why do many Americans find this basic pro-life case hard to accept? Philosopher Richard Stith nails the problem. They view the human embryo as something that is constructed rather than something that develops.2

For example, when does a car come to be? Some might say it’s when the body is welded to the frame, giving the appearance of a vehicle. Others insist there can be no car until the engine and transmission are installed, thus enabling the car to move. Still others point to the addition of wheels, without which a vehicle cannot make functional contact with the road. But no one argues the car is there from the very beginning, as, for example, when the first two metal plates are welded together. After all, those same metal plates can be used to construct some other object like a boat or plane. Only gradually does the assemblage of random parts result in the construction of a car.

According to a 2005 New York Times op-ed piece cited by Stith, most Americans see the embryo exactly the same way—as something that’s constructed part by part.3 It’s precisely this understanding, writes Stith, that renders pro-life arguments absurd to so many people. As they see it, embryos are no more human beings in early stages of their construction than metal plates are cars in the early stages of theirs.

Virginia Postrel, the former editor of Reason magazine, is a case in point. In a December 2001 Wall Street Journal op-ed piece defending destructive embryo research, she takes aim at pro-lifers who treat “microscopic cells with no past or present consciousness, no organs or tissues, as people. A vocal minority of Americans, of course, do find compelling the argument that a fertilized egg is someone who deserves protection from harm. That view animates the anti-abortion movement and exercises considerable influence in Republican politics.  But most Americans don’t believe we should sacrifice the lives and well being of actual people to save cells. Human identity must rest on something more compelling than the right string of proteins in a petri dish, detectable only with high-tech equipment. We will never get a moral consensus that a single cell, or a clump of 100 cells, is a human being. That definition defies moral sense, rational argument, and several major religious traditions.”4

Besides Postrel’s obvious category mistake (she answers a scientific question—“What kind of thing is the embryo?”—with appeals to non-scientific categories of morality, theology, and public opinion), the construction analogy she employs is deeply flawed. As Stith points out, embryos aren’t constructed piece by piece from the outside; they develop themselves from within. That is to say, they do something no constructed thing could ever do: They direct their own internal growth and maturation—and this entails continuity of being. Unlike cars, developing embryos have no outside builder. They’re all there just as soon as growth begins from within.  In short, living organisms define and form themselves. An oak tree is the same entity that was once a shoot in the ground, years before it had branches and leaves.

Stith illustrates the difference between constructing and developing this way:

Suppose that we are back in the pre-digital photo days and you have a Polaroid camera and you have taken a picture that you think is unique and valuable – let’s say a picture of a jaguar darting out from a Mexican jungle. The jaguar has now disappeared, and so you are never going to get that picture again in your life, and you really care about it. (I am trying to make this example parallel to a human being, for we say that every human being is uniquely valuable.) You pull the tab out and as you are waiting for it to develop, I grab it away from you and rip it open, thus destroying it. When you get really angry at me, I just say blithely, “You’re crazy. That was just a brown smudge. I cannot fathom why anyone would care about brown smudges.” Wouldn’t you think that I were the insane one? Your photo was already there. We just couldn’t see it yet.5

Likewise, whenever critics of the pro-life view describe the embryo solely in terms of its appearance, they fall into constructionism.  It’s an easy error to make. Our intuitions are not immediately impressed by the image of an eight-celled embryo with its dynamic self-directed development obscured.

However, our initial intuitions about the embryo can change dramatically upon reflection, as Stith explains:

When we look backwards in time or otherwise have in mind a living entity’s final concrete form, development becomes intuitively compelling. Knowing that the developing Polaroid picture would have been of a jaguar helped us to see that calling it a “brown smudge” was inadequate. If we somehow had an old photo taken of our friend Jim just after he had been conceived, and was thus just a little ball, we’d have no trouble saying, “Look, Jim. That’s you!” Thus the most arresting way to put the developmental case against embryo-destructive research would be something like this: “Each of your friends was once an embryo. Each embryo destroyed could one day have been your friend.”6

To sum up, human beings develop. To say they are constructed is simply false. I say more about this distinction and other pro-life arguments in my new book, The Case for Life: Equipping Christians to Engage the Culture.  In it, I contend that a biblically informed pro-life view explains human equality, human rights, and moral obligations better than its secular rivals and that pro-life Christians can make an immediate impact provided they’re equipped to engage the culture with a robust but graciously communicated case for life. Making that case is what this book is about. Get your copy today at or other favorite bookstore.


1. Keith L. Moore, The Developing Human: Clinically Oriented Embryology (Philadelphia: W.B. Saunders Company, 1998), pp. 2-18.

2. Richard Stith, Does Making Babies Make Sense Why so Many People Find it Difficult to See Humanity in a Developing Foetus, Mercatornet, September 2, 2008. 

3. Dalton Conley, A Man’s Right to Choose, New York Times, December 1, 2005.

4. Virginia Postrel, Yes, Don’t Impede Medical Progress, Wall Street Journal, December 5, 2001.

5. Stith, Ibid.

6. Stith, Ibid. Emphasis mine.