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Pro-Abortion Arguments: Fatal Flaws Part 2

By Stephen Napier Ph.D.

Abortion proponents have few arrows in their quiver, and the ones they do have are blunted. This is no more apparent than in so-called twinning arguments. Before outlining the argument it should be pointed out that the twinning argument is meant not to provide an argument for abortion, but rather to defeat certain anti-abortion arguments. Good anti-abortion arguments typically rely on a premise according to which I (a mature adult) was once an embryo. My embryo, fetus, infant, child…and me (now) are one and the same individual existing across different times and different developmental stages. Therefore, if I (now) have certain fundamental rights to life and I enjoy protection from being killed, so did my embryo since my embryo is fundamentally identical to me in terms of being the same individual as me. Twinning arguments wish to point out that the embryo is not an individual and therefore the embryo does not have the same fundamental rights as I do (now) since there is no fundamental identity between my embryo and me (now). I am an individual human person, my embryo is not – according to the twinning argument. Let us consider this argument close up.

The basic structure of such arguments is first to point out some empirical facts, and then to derive certain conclusions about the moral status of the embryo. The empirical facts are these: up to the 14-day point in an embryo’s development, he or she can divide, giving rise to another embryo (biologists call this identical twinning). At this point, proponents of the twinning argument try their hand at logic. They say, because the embryo can become two, therefore it is not an individual. Now clearly, this is what logicians would call a modal fallacy: the move from what is possible, to what is actual. To illustrate why this is a fallacy in this context, consider a starfish. If I were to chop the starfish in half, several weeks later I will have two starfish. But no one will say that before I chop the starfish in half, it is not an individual starfish. (Conversely, before I chop the starfish in half, we can all agree that it could become two.) Therefore, the fact that an organism can split into two, does not mean that the organism is not an individual. After all, we can ask before the split, “what is it that splits?” Our answer must be “that one organism of the sort homo sapien.” To be an individual requires there to be one countable organism of a certain sort. If the proponents of the twinning argument have a different notion of individuality, then they have not made this notion clear.

The proponent of the twinning argument may charge “uncharitable interpretation” or “straw man fallacy” at this point, indicating that I have treated the argument unfairly. I do not think I have. Any argument that argues from the empirical facts of identical twinning (some pre-14 day old embryos can twin) to the conclusion that the pre-14 day old embryo is not an individual, must employ other premises aimed to bridge the inference from x can become two organisms, to x is two organisms (or at least not an individual organism). There is no way of bridging this inference.

Concerning the empirical facts of the argument, it is an empirical fact that there is no organic life on earth that is ‘non-specific,’ that is, that does not belong to any particular species. In other words, all organisms living on earth belong to a particular species (even bacteria). We just don’t see unspecific, amorphous ‘life forms’ lying around. Therefore, the individual human embryo that will twin (within the fist couple of weeks of development) is human and, consistent with the argument presented above, is certainly an individual before twinning. How, then, to explain this phenomenon of ‘from one, two’?

The simplest way to explain (human) twinning is as a type of asexual reproduction, not unlike the starfish. Why? Because it happens that, during the first couple of weeks of development, our embryonic cells are still so plastic, dynamic and full of potential, that if the early embryo splits into two, the cells within each ‘half’ have the capacity to generate an entire new organism. As astonishing as this might sound to the non-scientist, long ago experiments have proven that when an early vertebrate embryo (for example, an amphibian embryo) is teased apart, each one of those cells has the capacity to generate an entirely new embryo, that will grow to be a normal individual of that particular species.

The twinning argument, then, instead of pointing away from the early human embryo being an individual, points to the early human embryo having the potential to generate a sibling through asexual reproduction.

© 2009 The National Catholic Bioethics Center