An ultrasound video of an unborn child sucking its thumb makes a case against abortion that reason hardly need supplement. But a zygote photographed just after an in vitro conception is not so easily recognizable as a human being or person. Pro-lifers often assume that this difficulty has been overcome by modern science. Since the 1820s, when evidence of ovular fertilization first became known, it has been clear that the life of a human being runs from conception to death.

Scientific knowledge that each of our lives began with conception, however, is insufficient to convince many people that an embryo is already one of us. Michael Kinsley, writing in 2006 in the Washington Post, expressed his utter bewilderment at opposition to embryonic stem cell research. “I cannot share, or even fathom, [the anti-research] conviction that a microscopic dot—as oblivious as a rock, more primitive than a worm—has the same human rights as anyone reading this article. . . . Moral sincerity is not impressive if it depends on willful ignorance and indifference to logic.”

Of course, Kinsley’s intuition that an embryo is “as oblivious as a rock” depends on his own obliviousness to what he must know about the embryo’s inner directedness and connection to its environment. To say that “embryos are merely ‘clumps of cells,’” writes Jon Shields, “tends to obscure scientific truth itself. This characterization suggests that an embryo is not biologically different than what we might find under our fingernails if we were to gouge a bit of skin from our arms. It is to imply erroneously that they lack coherence, integrity, and self-direction as ­organisms.”

The science behind Shields’s riposte is unassailable. But more is going on here than science. When a human embryo is visualized simply in terms of its current appearance, its ongoing self-development can easily be missed. No photograph can depict the inner self-direction of a growing embryo. Although biological science tells us a different story, the embryo looks like nothing more than an inert ball of cells. Its future development is hidden. This makes it seem reasonable to suppose that an embryo is not human. Scientific knowledge of its inner capability may not be enough to overcome this impression, for it is hard to imagine a nature or design utterly hidden from view.

There is a still greater difficulty. With repeated observation and a touch of scientific instruction, we can come to understand biological transformation. We can recognize a caterpillar to be a developing butterfly. Even so, it seems nigh impossible to think of a caterpillar as a particular or individual butterfly in the process of development. But this is how we have to imagine embryos if we are to do justice to their human development. We normally think of other creatures generically, as just a certain type of insect, for example, but we think of humans as specific ­individuals, albeit ones whose individuality may happen to be unknown to us. Because the embryo in the photo cannot (except arbitrarily) be ascribed any particular characteristics, it cannot easily be thought of as a developing individual. To say “This embryo can grow up to be an adult human being” is too abstract. We have all seen plain butterflies, but none of us has ever seen a plain (that is to say, non-individuated) adult human.

As pro-lifers we must be honest with ourselves and admit that there are limits to our ontological imagination, and that these limits are a barrier to full respect for human life, especially very early in pregnancy when the unborn child does not yet look much like the rest of us. However, there are ways to push back these limits and expand our imaginative understanding.

Although we have considerable difficulty recognizing future continuity of being, we have little or no difficulty in seeing identity-despite-change when looking back into the past. We may doubt that a new sprout, or a barren vine, is really a tomato plant. But once it bears tomatoes, we know that it was always a tomato plant. We may doubt that embryos are persons, but as we look back upon ourselves or upon our neighbors, we realize that we and they were all once embryos. An embryo in a photograph may at first seem no more than a grain of sand, but if that embryo snapshot had been taken twenty years ago, just after our friend Mary was conceived in vitro, we may well exclaim, “Look, Mary. That’s you!”

Some abortion supporters have acknowledged, regretfully, our capacity to see continuity of being and identity as we look back to the origins of each individual life in the womb. Philosopher Jeffrey Reiman, a defender of abortion, acknowledges that “we tend to read a kind of personal identity backwards into fetuses, and personal identity carries connotations of moral identity beyond mere physical identity.” Reiman adds, “Just because it is so natural to us to think that way, I believe that this ‘retroactive empersonment’ is the single greatest source of confusion in the abortion debate.”

Opponents of embryonic stem cell research (and early abortion) have also drawn attention to the continuity of identity we understand in hindsight. A few years ago, the United States Conference of Catholic Bishops produced an ad with a picture of a newborn baby and the caption, “270 days ago, Joshua was just an embryo.” The text went on to emphasize, “Embryonic stem cells . . . come with a heavy price tag: they are only obtained by destroying a living human embryo. An embryo like Joshua, 270 days ago.” In 2010, Irish opponents of embryo research put up billboards with photos of many stages of life, from embryonic to elderly, and the words “you. me. everybody. we’re all just grown-up embryos.

These ad campaigns make a fundamentally cognitive appeal, not an emotional one. They are attempts to wrap our minds more fully around human development as known to modern science, helping us overcome our difficulty in imagining that a very tiny organism can, with time, manifest itself as a mature human being. The ads work (insofar as they do work) by encouraging us first to look backward from fully developed human beings, where the continuity of identity is personal and easy to see, and then very quickly to begin with undeveloped embryos and think about how they are on a trajectory toward showing themselves to be the kind of people we know and love.

If we could somehow visualize facets of a still undeveloped embryo’s own future, our forward-looking intuition would become much more powerful. Here Kwame Anthony ­Appiah has made a very useful suggestion. He thinks Americans debating abortion should consider that “those dead fetuses could have been . . . their children’s friends.” Every friend is a unique individual. To see an embryo as a possible friend is thus to envision it as a human individual, even though nothing individual is yet known about him or her.

How much more transformative it could be if we could analyze an embryo’s genetic structure and conclude, “This embryo will grow up to be a petite Asian woman with considerable artistic talent.” Or better: Suppose a computer could someday produce images from her DNA and show us her likeness—even her very face—as a newborn infant, a little girl, a teenager, or an adult. Such an advance in technology might be as important as ultrasound for the pro-life movement, turning public opinion against the destruction of embryonic human beings. Real-time ultrasound images of fetal faces have already brought about more respect for prenatal life; how much greater might be the effect of faces with open eyes. Could we easily “look an embryo in the eyes” and decide to annihilate her?

This is not science fiction. The technological possibility of such images appears to be upon us. Forensic investigators are already using “DNA phenotyping” as a supplement to artists’ sketches in developing rough visual profiles of suspects, especially where no one has witnessed a crime but traces of unexpected DNA have been left behind. A recent story in the New York Times about the use of this technology contained examples of computer-generated faces paired with their actual counterparts. The resemblances may not be perfect, but they’re striking. Researchers are seeking to improve the accuracy of DNA-based visual profiles by adding ever more genetic variables.

If adult DNA can lead to a sketch of that person’s face, surely gestational DNA (obtained in a non-injurious way—from the placenta, for example) could be used to sketch the future face of an unborn child, for the content of the DNA in our cells changes but little during our lifetimes. We are, perhaps, on the brink of a new advance in the pro-life consensus, one not unlike that brought about by the now widespread use of ultrasound technology.   

Richard Stith is a research professor at Valparaiso University Law School. This essay includes an adaptation of a small portion of his recent article “Construction vs. Development: Polarizing Models of Human Gestation,” Kennedy Institute of Ethics Journal 24/4, 345–384 (December, 2014).