This is another example of a typical naive view of the problem with little awareness of the professional philosophical literature on the problem of reductionism (which is btw not necessarily tied to Christianity or religious apologetics at all). As philosopher Nancy Cartwright has argued pretty strongly (“Fundamentalism vs. the Patchwork of Laws”), it is a form of begging the question in favor of reductionism and “physics fundamentalism”. In short, the problem with this example is that we don’t know that the human body is nothing more than a bunch of billiard balls bumping together via Newtonian mechanics, and there is no experimental demonstration that this is the case, unless you simply assume a reductionist viewpoint that “because I can model the behavior of a few electrons, and the human body must have some electrons in it, thus I can fully deterministically model the behavior of the entire human body like I can with electrons.”
Yes, physicists are able to predict the behavior of a few particles pretty well. (Although, as anyone who’s familiar with even a bit of quantum chemistry knows, once you get away from the hydrogen atom things get super complicated very quickly and one must rely heavily on experimental data.) But unless you’re begging the question, that doesn’t say much about our ability to exhaustively, deterministically model larger complex systems. There’s even a case to be made that reductionism doesn’t always work in the case of diatomic molecules; there are some features of the molecules that have to be inputted by hand, based on experimental data. Finally, as some biologists argued to me just a few days ago (Some basic questions about genetic variation), the bottom-up, physics-based deterministic approach is actually discouraged when we’re trying to understand a biological cell. One simply can’t gain much insight into the behavior of biological cells by looking at the collective behavior of carbon atoms. Instead one has to look at the cells themselves. This is why the idea of “emergence” is a thing among many biologists and philosophers.
Please don’t misunderstand what I’m saying: I agree that if one can model the behavior of 10 billiard balls, then there’s good reason to expect that we can model 100 billiard balls using the same methods but just more computational power (i.e. drudgery). However, we don’t know that the human body is nothing more than a few trillion identical billiard balls obeying a set of simple laws like Newtonian mechanics. There could be (and probably are) other higher-level principles that come into play once you put together different types of “billiard balls” to form something else entirely, like cells and organs. These higher-level principles might not contradict the Newtonian physics of billiard balls, but they also might not be reducible to them. And without a strong philosophical or scientific argument it is not ridiculous to think that there could be some higher-level principles that are not reducible to them.