This article is from the archive of our partner .

OK, let’s go through this one more time.

Half of all pregnancies end in miscarriages, usually in the first couple of weeks, before a woman even knows that she is pregnant. A miscarriage destroys an embryo. If you believe that every embryo is the moral equivalent of a fully-formed human being, miscarriages are like a perpetual natural disaster like a flood or an earthquake, and you should be urging a massive effort to reduce miscarriages as the best way to save millions of human lives a year. As far as I know, there is no such effort going on in the United States or elsewhere.

But perhaps your concern is not the number of slaughtered embryos, but rather the morality of intentionally killing them or—worse, in your view—intentionally creating and then killing them. In that case, your attention should be directed to fertility clinics, which routinely create multiple embryos for each human baby they wish to produce. They pick and choose among the embryos that seem healthiest, and typically implant several in the hope that one—and not more than one—will survive. Every year tens of thousands of human embryos are created and destroyed (or pointlessly frozen) in the everyday work of fertility clinics. There is no political effort to stop this work. President George W. Bush even praised the work of fertility clinics in his speech announcing the policy that virtually halted stem cell research for eight years. Advanced fertility techniques have brought happiness to thousands of couples who otherwise would probably be childless. They are a godsend that no politician would dare oppose.

Of the tens of thousands of embryos discarded by fertility clinics every year, a few are used for stem cell research. Extracting the stem cells involves destroying the embryos, which would be destroyed anyway. True, the destruction of embryos used for research is purposeful, whereas the destruction of embryos in the everyday work of fertility clinics is incidental. But is that distinction really strong enough to support the difference between cavalier acceptance of tens of thousands of embryo deaths in fertility clinics and a legal ban on using a small fraction of these embryos to help develop ways to save lives? (Conflict-of-interest note: My life included. I have Parkinson’s.)

An embryo is not a fetus. It is microscopic—meaning, so small that you need a microscope to see it. It has no self-awareness, feels no pain, can’t give or receive love. Maybe you believe, despite all evidence, that the life of this microscopic dot has the same value as mine or yours when one of them must be sacrificed. But you had better be awfully sure that you’re right about this, and I don’t see how anybody can be that sure.

This article is from the archive of our partner The Wire.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.