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1 A Tale of Two Ontologies Introduction A Tale of Two Ontologies Are Humans Designated or Discovered? W hat exactly is the human embryo? At first blush, it seems odd that this question should be anything more than a purely detached matter for specialists in biology or philosophy. It may be a fair question, and an interesting one at that, but surely it should concern only those whose job it is to ponder such things. Yet there the embryo sits, at the very center of presidential councils , political campaigns, and culture wars; it is simply a fact that a good portion of our public discourse turns around this tiny axis, and hence answering the question “what is the embryo?” is of central importance to all of us and to our culture. How did something as small and seemingly insignificant as an embryo (smaller than the dot at the end of a sentence, it is often noted) come to play such an important role in modern society? Popular interest in the embryo surged in the United States with the 1973 Roe v. Wade decision. Once the Supreme Court concluded that access to abortion was a constitutionally guaranteed right, the general public took increased interest in exactly what was being aborted. Was it 2 A Tale of Two Ontologies a human? Or a clump of cells? Does that matter? And so on. The nature and moral status of the embryo has been a regular topic of debate ever since.1 From this already elevated level of interest, the question received another jolt with the isolation of human embryonic stem cells (“hESC” or “ES cells”) by James Thomson in 1998.2 Understanding Thomson’s achievement requires some knowledge of early human development (see figure 1). Upon fertilization of the oocyte (egg) by the sperm, a singlecelled entity—the zygote—is formed (A). Dividing rapidly, the zygote produces a number of smaller cells, known as blastomeres. A few short divisions later, by the second or third day following fertilization, the blastomeres have formed a ball-like structure known as the morula stage of embryonic development (C). Cell division continues, and by about day five, the embryo has grown to about one hundred or so cells, forming a fluid-filled structure known as a blastocyst, which possesses two distinct cell types (E). The cells that make up the outer layer of the ball are known as trophectoderm (TE) cells. Inside the ball is a cluster of cells, known as the inner cell mass (ICM). When extracted from an embryo and grown in culture, cells from the ICM are known as embryonic stem cells, and Thomson was the first to do this extraction successfully using human embryos. From a purely scientific standpoint, ES cells are of great interest to research scientists and doctors alike. They are the source of all the tissues in the body, and through the process of development they and their progeny organize themselves to take on the form of the body. Scientists have legitimate hope that studying ES cells will help them to understand development more fully. Medically, understanding how such cells differentiate into the various tissues of the body could lead to treatments for a wide range of ailments, from heart disease to Parkinson’s. Quite understandably the scientific and medical communities are intrigued by these possibilities. 1. See, for example, Hadley Arkes, Natural Rights and the Right to Choose (Cambridge: Cambridge University Press, 2004); or Patrick Lee, Abortion and Unborn Human Life, 2nd edition (Washington, D.C.: The Catholic University of America Press, 2010). 2. James A. Thomson et al., “Embryonic Stem Cell Lines Derived from Human Blastocysts ,” Science 282, no. 5391 (1998): 1145–47. A Tale of Two Ontologies 3 The difficulty in all this is that the extraction of ES cells either destroys the embryo outright or at the very least places it in peril.3 While this is only mildly disturbing when the embryo in question is a mouse or monkey embryo, the situation would at least seem to be different when the embryo in question is human. If the human embryo is indeed a human being, then there are quite serious concerns regarding its prop3 . Attempts have been made to extract a single cell from the ICM, thereby leaving the embryo intact. See, for example, Young Chung, et al., “Embryonic and Extraembryonic Stem A. B. C. D. E. F. zygote 2-cell morula early expanded fetus blastocyst blastocyst ICM TE Note: An earlier version of this...


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