Identical twins form when fertilized eggs split, sometimes weeks after conception. How does this work with ensoulment?

Reading Time: 3 minutes

Ensoulment is the proposed process of a soul becoming attached or associated with the physical matter of a human at some point in their development. For religious people, this is commonly understood to happen at conception when the sperm and egg combine.

We’ve already seen that IVF, with embryos being frozen by the million, can throw a spanner in the works for proponents of such ensoulment.

But it’s not just IVF that can cause problems. The development of certain twin embryos potentially also shows how the idea of a soul is broken.

Twins can develop in a number of ways. For example, fraternal (dizygotic) twins come from two separate eggs being fertilized and implanting. Identical (monozygotic) twins are formed when one already-fertilized egg splits in two.

Most identical twins come about when the fertilized egg splits at the two-cell stage. Mirror twins (one will be right-handed, the other left, and so on) are formed when the split happens around day 5 or so. If the split happens after day 10, conjoined twins will form. This can even happen at day 13 or 14.

It’s almost as if the idea of a soul was dreamt up before we understood how life and biology works, with the theological ideas being square pegs rammed into round holes…

I’m sure the eagle-eyed reader has predicted the issue for ensoulment proponents. If the soul is generated in some way at conception, then what happens to this soul when the “human” at this early developmental stage splits?

We have a number of cells to which a soul attaches or from which a soul emerges. The soul somehow has meaningful connection to or reflection of that physical matter. And yet, this matter splits in two to lead to two different individuals (even if they are conjoined, though there are interesting debates about what “individuality” means here). In the most extreme cases, there can be over 15 days of a soul existing with its early developmental human before the human splits.

But even after only one day, a split will generate the same problem.

What happens? Does the soul split in two? Does another soul just get added on by God as a band-aid afterthought? Does God predict this scenario and attach two souls to one individual and then allow one to jump onto one-half of the newly split cells?

Of course, the most obvious answer to this conundrum is to eliminate the problem: Souls do not exist. With naturalism, we do not need to explain what happens in this bizarre situation of ensoulment because ensoulment is not a thing. This is Ockham’s Razor: We prefer the simplest explanation with just as much explanatory power and scope that does not unnecessarily multiply explanatory entities.

By creating the notion of a soul (which, don’t forget, is enshrouded in terminal philosophical issues), the believer necessarily creates more problems, problems that are unsolvable—or certainly unevidenced. After all, how can you support a solution to a problem with evidence if the subject of the problem (the soul) lacks any evidence to support it?

It’s almost as if the idea of a soul was dreamt up before we understood how life and biology worked, with the theological idea being a square peg rammed into a round hole…

The soul just doesn’t work as a coherent idea.

Not only do we really not know what a soul is and what it does (that isn’t already explained by some other aspect of the human body and brain), but we don’t know how it works with being causally responsible for human behavior so it can reasonably transfer reward and punishment into the afterlife. And these further issues with IVF and egg splitting throw the whole idea into the realms of terminally problematic.

While you might soundly say that you have soul, based on my research, I can soundly say that you most certainly don’t.

Jonathan MS Pearce

A TIPPLING PHILOSOPHER Jonathan MS Pearce is a philosopher, author, columnist, and public speaker with an interest in writing about almost anything, from skepticism to science, politics, and morality,...