Is the Prime Mover a “God of the Gaps” Argument?

Recently, a question was posed to me about several possible problems with the Prime Mover argument for the existence of God.

For those unfamiliar with the argument, you can follow the link above to the full articles I’ve written explaining/defending it. Here is an extremely condensed, outlined version of it:

1. Our senses observe that motion really exists
2. Motion is a potency reduced to act
3. Potency can only be reduced to act by another which is itself already in act
4. Essentially ordered series of such motion must either terminate in a prime mover (which is Pure Act), or else have a circular or an infinite regress
5. Essentially ordered causal series of such motion cannot in principle have a circular or an infinite regression
6. Therefore, there must exist a prime mover, which is a being of Pure Act

The first possible problem  is that the argument commits the logical fallacy of a “false dichotomy” that premise 4 is a false dichotomy. A false dichotomy, also known as a false dilemma, is when a statement presents certain options as if they are the only possible options, and forces you to choose between these options. A simplistic example would be as follows:

1. A person’s favorite flavor of ice cream must be either vanilla or chocolate
2. John’s favorite flavor of ice cream is not vanilla
3. Therefore John’s favorite flavor of ice cream must be chocolate

Obviously this is fallacious, because there are many other ice cream flavors than just the two presented that one could hold as a favorite. The argument, however, wants to force us to choose between these as if they are the only possible options.

In general, whenever an argument asks us to choose between possible options, it is wise to examine carefully for this fallacy. One way to do so is to check whether the options presented are  jointly exhaustive. Options are jointly exhaustive when they together cover the entire range of possibilities in a given set. The example above is not jointly exhaustive, because it is asking us to choose between the set “ice cream flavors” but fails to include all the possible species within this genus.

While we should always be careful in relevant situations to check arguments for committing this fallacy, we also must be careful that we do not falsely accuse arguments of containing a false dichotomy, just because the argument asks us to choose between various options. Consider this humorous example (courtesy of my logic professor):

1. Everything that exists is either a Hippopotamus or a Non-Hippopotamus
2. An elephant is not a Hippopotamus
3. Therefore, an elephant is a Non-Hippopotamus

This argument divides the set of “all existing things” into those existing things which are Hippopotami, and those which aren’t Hippopotami, the latter being obviously an almost infinitely larger category, since everything else in the entire universe that isn’t a Hippopotamus fits into it. The premise may be non essential and utterly useless, but is is jointly exhaustive of the entire set of “all existing things,” so it is not a false dichotomy.

The person responding to the Prime Mover argument claimed that premise 4, however, is  false dichotomy, because, supposedly, it leaves out another possible option. What possible option is that? According to this person, another possible option is “something not yet discovered” that we just don’t know about as of now.

Which leads to a related second problem posed with the argument: It’s a “God of the Gaps” argument. I’ll respond to each of these objections in order.

First, is premise 4 actually a false dichotomy? Premise 4 states that “essentially ordered series of motion must either terminate in a prime mover (which is Pure Act), or else have a circular or an infinite regress“.

The premise does indeed present us with a number of options in the set of “possible explanations for essentially ordered causal series of motion” and asks us to choose between these options. To be fair, the outlined version of the argument that I presented does contain a number of “implicit premises,” but that is because they are explicitly drawn out and explained in the full articles. For example, I just assumed in the outline version that the prime mover is Pure Act; which is not obviously true but is defended at length in the full articles. To make up for this, however, for the purpose of logical clarity, I’ll restate the premise as such: Essentially ordered series of motion must either terminate in a prime (first) mover, or else have a circular or an infinite regress.

In this premise, a “prime mover” is just any first causal member of a series; the premise alone does not establish that the prime mover is pure act. In this sense, my brain is a “type” of prime mover in the causal series of me waving a stick: the motion of the stick is caused by my hand, the motion of my hand is caused by my arm, the motion of my arm is caused by muscle contractions, the muscle contractions are caused ultimately by neurons firing in my brain. These neurons are the “prime mover” relative to that causal series (although the causal series actually extends much further down than that, to the atoms, subatomic particles, and ultimately to God, but this is just for the sake of illustration). In the causal series of a carpenter crafting a table, the carpenter is likewise the “relative” prime mover of that particular series. A prime mover, in a general sense, is just the first, or most fundamental, causal member of a series.

With this having been made clear, let’s return to the options in the premise: essentially ordered series of motion must be explained either by a prime mover, an infinite regression of movers, or a circular regression of movers. The objector, however, claims that these options leave out a legitimate possibility: something not yet discovered.

Unfortunately, that’s not how the false dichotomy fallacy works. You could claim the same thing of just about any argument. Consider the Hippo argument above; we could just as easily claim that this argument commits the false dichotomy fallacy, because there might be something that exists somewhere in the universe that we haven’t discovered yet that’s neither a Hippo nor a Non-Hippo; which is just absurd! Logically, the categories we’ve created of Hippo and Non-Hippo, as silly as they might be, cover the entire range of possible existing objects. To say otherwise would be equivalent to saying that the categories “things that exist” and “things that don’t exist” likewise fail to cover all of the possibilities, because there might be some strange sort of entity yet to be discovered that neither exists nor doesn’t exist.

But the examples I’ve given here are rather extreme. Let’s suppose we come across another argument not as explicitly logically exhaustive as the form “X or Non-x.” Here’s a potential example:

1. Every mammal is biologically either male or female
2. Clifford the Big Red Dog is not a female
3. Therefore Clifford the Big Red Dog is a male

Now, the options “male or female” are not as explicitly logically exhaustive as “male or non-male,” so one could perhaps make the claim that it is a false dilemma, because it leaves out the possibility of some super rare species of mammal yet to be discovered which evolved completely differently from all other mammals, having a biological gender that can’t be categorized as either male or female. Such a phenomenon is theoretically possible, but surely we wouldn’t therefore consider the argument above as logically fallacious. “Male and female” might not be logically exhaustive in a theoretical sense, but we’re safe in using them as logically exhaustive if the set we use is “biological genders of mammals known to exist.” Until an exception to the rule is found, the rule should be regarded as sound.

But that is only relevant in cases wherein the options might not be obviously logically exhaustive. Premise 4 of the Prime Mover argument, however, is obviously logically exhaustive, based on the very nature of causal series. A causal series is just a series whose members include at least one instance of cause and effect.

For an example, let’s consider a genealogical line. A man is the effect of the cause of his parents. His parents each in turn are the effects of the causes of their own parents. And so on and so on. This is a genealogical causal series. What are the possible explanations of the series? One theoretical option is that the series just goes back forever. Each person is caused by his parents before him, who are caused by their own parents, and so on, reaching back infinitely, with no “first humans” who started the series. The series has just always been going. This is an infinite regression.

The next option is a circular regression. A circular regression looks like this: A is caused by B, B is caused by C, C is caused by D, D is caused by A. And so on. The series forms a loop, wherein each member is still the effect of the preceding member, but the series does not stretch back infinitely, it just exists in a continuous loop. Important to note is that in such a circular series, A is effectively the cause of itself.

The final possibility is that the series neither stretches back infinitely, nor exists in a continuous loop, but rather terminates in a first member. To go back to our example of genealogy, this would be like positing a number of “first humans” who are the ancestors of all other humans. They are the relative first members or “prime movers” of the causal series (of course, in reality, these first members themselves, even though they are the first humans, would have been caused by something else, so the series would continue; but we will refer to them as such just for the sake of analysis).

So these are the three options presented in the argument: infinite regress, circular regress, or termination in first cause. In order to establish it as a false dichotomy, we would have to find some other possibility that fits within the set but is not covered by the above. Is there another possibility?

Well, perhaps we might posit a scenario in which the causal series splits and branches off into several different series. After all, most causal series don’t actually just extend backwards in a straight line; but rather are a complex web of interlocking cause and effect relationships. Is this another possibility not covered by the three original options? No, because the premise just refers to a causal series; it does not exclude the possibility of a series splitting into multiple other series, but just states that each of these further series will all either terminate in their own first cause, extend in infinite regress, or loop in a circular regress. Note also that a “first cause” does not necessarily entail “one being” as that first cause; the relative “first cause” of a human is actually two entities: both of his parents (although the ultimate first cause, as the prime mover argument demonstrates, is one).

Besides this, there don’t seem to be any other possible options. A causal series, by its very nature, will either terminate in a first cause, regress infinitely, or regress circularly. These options seem to be completely logically jointly exhaustive. It simply won’t work to posit that there might be some other logical option we just don’t know about; that’s not how it works. In general, asserting that an argument commits the fallacy of false dichotomy only works if there is some actual known logical possibility missing; or else, if there are some actual reasons for thinking that the options given are insufficient. Otherwise you could just claim that any disjunctive syllogism is a false dichotomy, which is absurd.

Which brings us to the next objection: that the argument is a “God of the Gaps” argument.      A God of the Gaps argument is an argument which starts from some lack of knowledge in some particular area, and then infers God as an explanation for this lack or “gap” of knowledge. It is a favorite accusation against theistic arguments of many “new atheists,” such as Richard Dawkins. Christian philosopher Randal Rauser recently wrote a blog post on this same issue, focusing on the derisive quip “godditit” as a means to shut down/invalidate any theistic argument before it even begins.

Now it is important to understand what exactly the God of the Gaps fallacy is, and what it isn’t. There are certainly theistic arguments which commit this fallacy, and these arguments should rightly be considered illegitimate. But just the fact that an argument infers to the existence of God as best explanation does not mean that it has committed the God of the Gaps fallacy. If we rule out all arguments which infer to God’s existence as fallacious, just because they use God as an explanation, then we in fact have committed the fallacy of question begging, because we have ruled out the possibility of theistic explanation from the very beginning. So how can we tell whether or not an argument is a God of the Gaps argument?

A God of the Gaps argument infers from a lack of knowledge, or from a particular ignorance, to a supernatural explanation. A simplistic example would go like this:

1. We don’t know how life originated on earth
2. Therefore God must have done it

This is obviously a very poor argument, but why exactly? The type of reasoning going on here is called abduction, or inference to the best explanation. Abduction reasons from some fact or data to the hypothesis/theory which best explains that data. Notice that in the God of the Gaps argument, however, we aren’t reasoning from some positive fact/piece of data, but rather from a lack or absence of fact/data.

Now, this in itself is not always or necessarily fallacious. We could potentially take the exact same argument from above and turn it into a much stronger abductive argument, like this:

1. The origin of life on earth is inexplicable via physical laws/purely natural means
2. Therefore, since physical laws/purely natural means are unable, or at least highly unlikely, to explain the origin of life, the best explanation is some supernatural cause

This argument may or may not be any good, depending on the truth of premise 1 and the likelihood of competing theories (I’m not trying to defend it, just offering it as an example). But what it’s not is a God of the Gaps argument, unlike the previous example. The first version inferred from a gap in knowledge: we don’t know how X works, therefore God is probably the explanation. The second version argued from a positive piece of data: X is physically impossible via purely natural means, therefore the explanation of X is probably not purely natural means. The first is God of the Gaps, the second isn’t, regardless of its overall strength.

A classic representation of God of the Gaps reasoning is ancient Greek mythology (although this is, again, extremely simplistic): We don’t know how the sun rises and sets, so it’s probably a god pulling a sun chariot. That’s God of the Gaps.

Now, the objection posed to me is actually based on the assertion that premise 4 of the prime mover argument is a false dichotomy. The objector claimed that since another possibility is some unknown option, then to choose one of the three original options is to just try to “fill the gap” in our knowledge.

For one thing, this doesn’t work because we’ve already shown that premise 4 does not commit the fallacy of false dichotomy, that the options given are indeed logically jointly exhaustive, and that it’s illegitimate to accuse an argument of false dichotomy on the basis that “there might be some other unknown possibility.”

But let’s say, just for the sake of argument, that the original objection is legitimate. Let’s say that we then reformulate the premise as such: Essentially ordered series of motion must either terminate in a prime (first) mover, extend in a circular or an infinite regress, or else be explained be some as of yet unknown option.

What would a God of the Gaps argument look like here? Something like this:

1. We don’t know what explains the causal series of motion
2. Therefore a prime mover must be the explanation

Again, this argues from our lack of knowledge to a random explanation. This would be fallacious. But that’s not what the prime mover argument does, at all. In the full article I laid out reasons why essentially ordered causal series of motion cannot in principle have an infinite or circular regress, and why it necessarily must terminate in a first cause/prime mover. Whether or not the argument actually works (I think it does), it most definitely does not commit a God of the Gaps fallacy.