Excursus on Natural Theology (Part 1): Definition of Natural Theology

1.0  Definition of Natural Theology

Today we are turning to a new section in our survey of Christian doctrine. We are in the midst of the study of the doctrine of God. We have completed our subsection on the attributes of God. Now I want to leave our doctrinal outline and take an excursus into the subject of natural theology.

What is natural theology? Natural theology can be defined as that branch of Christian theology which seeks to explore the justification of belief in God apart from the resources of authoritative divine revelation. Natural theology, as the name suggests, is what we can learn about the existence of God apart from the resources of authoritative divine revelation.

One might ask, how are the arguments of natural theology related to general revelation? You will remember that in our study of the doctrine of revelation we saw that God has revealed himself both generally in nature and conscience as well as specially in his Word and in Jesus Christ. Through God’s general revelation in nature and conscience we can have a general knowledge of God as the Creator and Sustainer of the universe.

Are the arguments of natural theology the same as general revelation? I don’t think so. God’s general revelation is his self-disclosure in the created world that He has made. It is, as it were, the fingerprints of the potter in the clay or the telltale traits of the artist in the painting he has made. It is His self-disclosure to us in the created order. Natural theology, on the other hand, is the result of human reflection upon the created order and upon God’s general revelation. The arguments of natural theology are thus human constructs. These are not divinely given. Therefore, they are fallible and could well be unsound. Every generation will be called upon to refurbish and update and develop arguments for God’s existence based upon the knowledge that they have. So natural theology is not static. It is an evolving project that is constantly renewed.

Therefore, you can feel free to disagree with any of the arguments that are shared in this section on natural theology. These are not divinely given. If you think that these are unsound or weak arguments, feel free to reject them. But I hope that you will find that at least some of these arguments are pretty good arguments for God’s existence.

There has been a renaissance of interest in the subject of natural theology over the last half century or so in Anglo-American philosophy. As a result of the renaissance in Christian philosophy that has been taking place over the last several decades, there has also been renewed interest in the project of natural theology. In fact, I have here one such manifestation of that interest. This is the Blackwell Companion to Natural Theology published by Wiley-Blackwell in Oxford in the UK. This is a volume, as you can see, of considerable size that contains essays by some eleven different philosophers on different arguments for God’s existence. This is some of the most sophisticated natural theology that is available today. This is not a book for beginners. If you are a beginner, you can start with something like On Guard. But this is book for professional philosophers, theologians, and scientists.

In our study in this class, we are going to examine principally six arguments for God’s existence that I have worked upon personally and find especially interesting. But as the Blackwell Companion indicates, there are many more as well.

In doing natural theology, I want to emphasize the importance of developing a cumulative case for the existence of God. We shouldn’t think that the existence of God depends upon any single argument. Rather we ought to think of the arguments as providing cumulative evidence. Each argument reinforces the others so that the cumulative case for God’s existence, I think, is very strong. This is important because even if an argument taken in isolation is not a very strong argument, nevertheless, it could be part of a cumulative case for God’s existence that would warrant belief in God.

I think the perfect analogy here will be a case offered in a court of law, where the prosecution will bring all manner of evidence to try to show that the accused is guilty. Any single piece of evidence might not be convincing. The fingerprint evidence could be explained away. The eyewitness testimony may not be decisive. Perhaps one can identify a motivation that would have led the accused person to commit the crime, but that alone wouldn’t serve to convict. Nevertheless, taken together the cumulative force of all of these considerations could make it beyond a reasonable doubt that the accused is guilty.

In exactly the same way, the arguments of natural theology should not be just considered in isolation but rather as part of a cumulative case. For example, the ontological argument may strike you as based upon a premise that is reasonable and plausible but not one, you might think, for which you have a compelling reason to believe. You could just as easily perhaps deny it. Or you might think that the cosmological argument from the beginning of the universe taken alone wouldn’t prove that God exists, but perhaps taken in conjunction with the argument from the fine-tuning of the universe, the combination of the beginning of the universe and its incredible fine-tuning would lead you to think that it is more plausible than not that a personal Creator and Designer of the universe exists. You might think that the moral argument alone is not sufficient to justify belief in God, but you might think that the moral argument taken in conjunction with the argument from contingency and the ontological argument present a good case for belief in God.

So don’t think of the arguments of natural theology as links in a chain. A chain is only as strong as its weakest link. Rather, think of the arguments of natural theology as a coat of chain mail where the coat of mail is stronger than any single link because all of the links reinforce one another, so that the coat of mail can be very strong even if there are individual links in it that are weaker.

Nevertheless, it seems to me that if each argument can be shown in isolation to be a good argument for God’s existence, then your cumulative case is going to be all the more powerful. If, for example, the DNA evidence is decisive for the guilt of the accused and you’ve also got independent eyewitness testimony from people who were in a position to see what happened and you’ve got, say, video evidence of the person actually committing the crime, any one of these would be sufficient for conviction. Taken together, they make a really overwhelming cumulative case.

What I’ve tried to do in defending these arguments is to consider them in isolation and show how each one, even taken alone, is a good argument. Then so much the stronger when part of a cumulative case!

I formulate the arguments deductively for the case of simplicity and clarity. That is to say, I formulate them in terms of some simple premises which then lead logically to a conclusion. The advantage of doing it this way is, as I say, it makes them makes them very clear, makes them very simple to grasp, and makes them easy to memorize and share. You can ask the person who is skeptical of them which premise he rejects and why, because if he can’t identify a false or unjustified premise, then if the argument is logically valid, he has got to agree to the conclusion.

In these deductive arguments, what we have to do is to formulate arguments that will meet a number of conditions for being a good argument.

First of all, the argument needs to be logically valid. That is to say, the conclusion needs to follow from the premises according to the rules of logic. There are only about nine basic rules of inference that govern all reasoning. We can construct arguments for God’s existence using these rules of logic to derive conclusions. A good deductive argument would need to obey the rules of logic – it needs to be logically valid.

In addition to that, the argument also needs to be sound. That is to say, the premises of the argument need to be true. It is not enough just to have a logically valid argument; it also needs to have true premises. If you have an argument which obeys the rules of logic and has true premises, then it is guaranteed that the conclusion is true. The conclusion necessarily follows by the rules of logic from the true premises and therefore is also true.

But it is not enough just to have a sound argument. The premises also need to have some sort of warrant for us or some sort of evidence whereby we know that they are true. Otherwise, it is trivially easy to formulate arguments for God’s existence. For example, you could have an argument like this:

1. Either the moon is made of green cheese or God exists.

2. The moon is not made of green cheese.

3. Therefore God exists.

That is a sound deductive argument. Each of the premises is true. Consider (1): Either the moon is made of green cheese or God exists. Since God does exist, that premise is true. For a disjunction to be true only one of the either-or statements needs to be true. Premise (2) is also true – the moon is not made of green cheese. Therefore it follows logically that God exists. So is this a good argument for God’s existence? I don’t think you will find it in any apologetics textbook. Why not? Because the only reason you would believe the first premise is because you already believe the conclusion. The only reason you believe that either the moon is made of green cheese or God exists is because you believe the conclusion “God exists.” You are reasoning in a circle. This is called “begging the question” or “circular reasoning.”

The reason for believing the premises cannot be that you believe the conclusion, or you are guilty of begging the question. You need to have some sort of independent evidence for the truth of the premises.

Here is where things get controversial. How much evidence for the premises do you need in order for the argument to be a good one? Many times atheists will demand that you have compelling evidence for the truth of the premises. If it is even rational not to believe the premise, then the argument is a failure. For an argument to be successful (they claim) the evidence must compel belief in the premises. But the vast, vast majority of philosophers would say that that sets the bar for success far too high. In that case there are no successful arguments for anything of significance or importance. In order for the belief in the premises to be justified or warranted, the evidence doesn’t need to be compelling.

How strong does the evidence have to be? This is controversial. It is hard to say. Some people would say as long as the evidence is just sufficient to give you rational permission to believe the premises – that is enough for you to have a good argument and for your belief to be rational. If the evidence is such that you are permitted to believe the conclusion on the basis of the evidence, then that is enough.

I am inclined to a somewhat stronger view, to say that the evidence should make the premises more plausible than their negations. If the evidence makes the premises more plausible than their contradictories, then the rational person should believe the premises rather than the contradictories. They don’t need to be certain. They don’t need to be highly plausible. They just need to be more plausible than their opposites.

Some will say that that is not sufficient for a good argument because perhaps each premise taken individually is more probable than its negation, but nevertheless when you consider the premises collectively maybe they are not more probable than the negation of all of them. But in that case we can say, at least, that the conclusion of a deductive argument cannot be lower than the probability of the premises taken together. So if, for example, the premises taken collectively have a probability of 40%, then the conclusion of the argument is at least 40%, but it could in fact be higher.  The collective probability of the premises merely sets a lower bound for the probability of the conclusion.  If the premises of a deductive argument taken together have a probability >50%, then the conclusion is guaranteed to be more probable than not.

I think that you’ll find that the arguments I present meet that higher standard. For example, consider the kalam cosmological argument:

1. Whatever begins to exist has a cause.

2. The universe began to exist.

3. Therefore the universe has a cause.

It seems to me that the first premise Whatever begins to exist has a cause is virtually certain. So the real crux of the argument will be the plausibility of the second premise – that the universe began to exist. The probability of the conclusion will be virtually identical to the probability of the second premise. The goodness or the cogency of the argument will not be reduced by any uncertainty attending the first premise. In all the arguments that I shall present, I think that the collective probability of the premises of each argument is greater than 50%, so that the argument is guaranteed to be a good one.