Greg Bahnsen’s Critique of Natural Theology

Notes from Greg L. Bahnsen’s lecture, “Philosophy of Christianity-Critique of Natural Theology.”

Natural Theology is the outlook that by correct use of reason and evidence, the unregenerate man can without assistance arrive at elementary religious truths. To put it another way, autonomously a man may come to a proper interpretation of God’s revelation in nature and history autonomously. The mind of the natural man has sufficient rational powers to discover God on his own.

Five problems for natural theology
1) It holds that some partial elements of the truth about theism can be reached at the end of an autonomous reasoning process.
-By contrast, Scripture says that the full truth about God is objectively visible from the very start (Romans 1)

2) It thinks that the unbeliever can be fair and open-minded and use right reason and will affirm a portion of religious truth upon the strength of the evidence.
-Scripture views the unbeliever prejudiced about God, having a pre-judgment against the God of the Bible. He is closed-minded and suppressing the truth in unrighteousness.
-Only grace takes evidence and makes it plain to the eyes of the sinner

3) It portrays men as able to interpret natural revelation correctly aside from special revelation.
-Scripture teaches that special revelation is the divinely ordained means for correcting the sinner’s outlook on the world. The Scriptures gives us the only presupposition that can account for the created reality correctly.
-Nature must be read through the spectacle of Scripture.

4) It is necessary for the Holy Spirit to work for blinded eyes to see the truth. If the Holy Spirit works, he makes us submit to the whole truth of God– we submit to God as Creator, Judge and Redeemer.
-natural theology teaches that you have a certain fundament of truth that are founded upon reason, on top of this, we can build the house of faith. We first prove a generic god exists and then prove the Biblical God.

5) Natural theology has not correctly assessed two major considerations: a) the proper use of reason b) nature of unregenerate reason
a) proper use of reason
-it doesn’t see the nature, range and purpose of reason in the whole counsel of God
b) nature of unregenerate reason
-it does not see the autonomous rebellion nature of unregenerate reason

A proof of God’s existence is too easy and yet too impossible to give
First of all, the idea of proving God’s existence is in one sense too easy.

Here is a sound and valid proof of God’s existence:
Disjunctive Syllogism
P1. Nothing exists or God exists
P2. Something exists
C. Therefore, God exists

You cannot defeat this argument. Let’s look at it, is this a sound argument? Well it’s certainly a valid argument. Testing for validity always deals with the form of the argument.

Let’s test for validity (form):
P1. P or Q
P2. Not P
C. Therefore, Q

This by the way is a valid argument; it is called a disjunctive syllogism. If it is true that at least P or Q is true and one of them is shown to be false, consequently the other one must be true. Let’s begin with the minor premise: something exists. Does anyone have any doubt about this? Is the first premise true?

The first premise is true as long as one of the disjuncts is true. Well it is false if God does not exist and it is true if God does exist. One can reject P1. only if atheism has been proven. Since there are no good proofs for atheism we have no difficulty accepting that P1. is true, so if P1. is true, we have a valid argument with true premises. P2. just needs to cancel the other disjuct in P1. If P1. is true, consequently God must exist, because P2. shows that the first disjunct in P1. cannot be true.

Objection: One will say that you must prove that God exists before you accept P1. But how is a defect in the argument itself. It might be a defect in us or those who don’t accept the argument, but the argument is a good one. Them not knowing sometimes just means the argument is ineffective for them. They are looking for a convincing argument, but we are talking about the validity and soundness of the proof itself.

Can we give an argument that will convince people?
I don’t think anyone can construct an infinite series of arguments for each premise in his argumentation. Let’s say we have an argument up here and in order for it to be convincing, we have to have an infinite series of arguments for each premise offered. We have:
P1. P or Q
P2. Not P
C. Therefore, Q

Now if this is going to be a convincing are you laying this condition on me that I have to prove P1. and P2. by another argument. Let’s say I use argument A to prove P1. and I use argument B to prove P2., but you might not accept arguments A or B. So no I must use argument C to prove A and D to prove B. I can keep going on and on. Are you saying a convincing argument has an infinite series of proofs behind it?

We can demand however that proof in some particular case if some termination rule for such demands is recognized by all the participants in the discussion. Let’s say we all got together and agreed on a termination rule. That is, it won’t be an infinite series of arguments, we will all agree that we have reached proof once we reached a certain point. The series of challenges and replies will end when the soundness of the rule is known to all the participants. Let’s say we get this room filled up with Christians and non-Christians and our termination rule is that when everybody that is party 2 in this challenge and reply process, when everybody knows the soundness of the proof, then the proof is terminated. The problem with this is that it makes the whole idea of proof relative. Relative to the people in the room. If you get a bunch of 4 year olds in the room then the proof might terminate soon. If you get a bunch of PhD philosophers then you won’t prove anything ever! The termination will be relative to the people in the room.

It seems unprofitable to speak of an argument proving its conclusion to someone who knows the truth of its premises from his own a priori knowledge of the truth of its conclusion. It turns out your willingness to accept P1. is really conditioned upon your a priori willingness to accept the conclusion. If you know the truth of the conclusion, you’ll accept that premise. Not only is the argument a good argument, it is also convincing. But such an argument would not enable you to learn anything new. So let’s put a new condition of theistic argumentation. We may say that an argument is convincing if 1) it is cogent (valid in form, true in premises) for a particular person 2) if that person knows that the premises are true without inferring that truth from the conclusion. This would be a convincing proof. A proof in this sense is person-relative who sees its cogency and what the person is and is not able to know and infer from things.

Remember I showed you how easy it is to prove God’s existence and yet how impossible it is to give a convincing proof of God’s existence? What morals can we learn from what I’ve talked about so far.
1) An argument can have help us to advance our knowledge only if we already know something. Nobody can gain all of his knowledge by proofs. Somebody could suggest that then we could know God even though we can’t prove His existence. So even we couldn’t prove God’s existence, there wouldn’t be a defect in the knowledge of God.
2) It’s not likely that there is some argument out there that will prove God’s existence to everyone. The reason is because it is highly unlikely that there is a set of propositions that is known by everyone. A set of propositions that is known by everyone that entails God’s existence. On our conception of convincing proof, you must have a certain knowledge of premises. If there is going to be one set argument that proves God’s existence for everyone, then there must be a set of premises which are known to everyone. Moreoever, there must be a set of premises known by everyone which implies God’s existence. Apart from the knowledge of God and His attributes, I don’t know of any premises that are known to everyone. It is just this ridiculously hard task that many unbelieving philosophers are demanding of us. They are demanding that there be one argument that will be convincing to everyone. But I don’t believe the ignorance of unbelievers should be a barrier to our own intellectual advance. The fact that not everyone knows the premises necessary to prove God’s existence as we would as believers is not necessarily a defect in our argument.
3) Likewise, it is very unlikely that there is some conclusion that can be proved to everyone by some argument or another. By point a minute ago was that there is no one argument that will work for everyone. My point now is that there is no one conclusion that can be proven for everyone. The epistemological question about proofs for God’s existence is in the long-run dependent upon the metaphysical question about the existence of God itself. Whether people will accept the proof will depend upon the basic worldview in which they are thinking. It is a mistake to think we can answer the epistemological question about proving God’s existence prior to answering the metaphysical question whether God in fact exists. Whether there can be a proof of God’s existence depends upon whether He actually exists. If He does, then there can be a convincing proof, if He doesn’t, then there cannot.

Historically, the theistic proofs have not proven a biblical conception of God
The theistic proofs might give us an impersonal principle and not a personal god. They might give us a finite god and non-transcendent god. Perhaps the proofs might give us a plurality of gods. Perhaps there are lots of gods causing things in this world instead of one First Cause. The appeal of the theistic proofs is almost always about the probability of God’s existence. The Bible says that everyone knows that God exists, because He has revealed Himself to everyone (Romans 1).

Methodological Errors of Natural Theology
1. Who would you be constructing a theistic proof for? Someone who doesn’t believe in God. Romans 1 tells us that there are no atheists. If there are no atheists, then there refusal to confess that there is a God is a suppression, not a matter of ignorance. They don’t have an intellectual problem; they have a moral problem that they deny God’s existence. Natural Theology proceeds on the assumption that man just needs more information, that the world can be understood apart from the revelation of God and that reason is operating fairly normally as it is.

2. It assumes that the facts of the world are brute facts. That they don’t have to be put within an interpretive context to be understood at all.

3. It assumes the abstract nature of logic, that logic is simply the imposition of mental categories on the flux of experience.

4. It assumes that common ground can be had with the unbeliever without having sense of antithesis, that we and the unbeliever know the same thing, in the same way and with the same heart and mind attitude. They say from this, we can move on to prove God’s existence.

5. It assumes the open-minded neutrality of unbelievers.
-but the Bible teaches they are not open-minded or neutral. The Bible teaches that we ought not to be netural and we ought to surrender our full commitment of mind and body.

We must rather reconstruct the theistic proofs along presuppositional lines.
We want to show that the unbeliever is suppressing the truth by arguing about our worldviews. Instead of saying, “let’s take this particular fact about the world and see if it leads us to God”, what we do is say,”What is your total outlook on life and let’s see if that can get us to knowledge about anything.”

First, we argue about worldviews.
Second, we argue from the impossibility of the contrary. We contrast the worldview of the unbeliever and worldview of the unbeliever showing that the unbeliever’s worldview is impossible. It is impossible because it leads to dialectical tensions and that he suppresses the presence of God as it is seen in His nature, creation and providence of God. You will see that nature of God corresponds to the Ontological Argument, creation responds to the Cosmological Argument and providence of God corresponds to Teleological Argument. What I’m asking you to do is put these arguments in a presuppositional framework. What we challenge the unbeliever to do is to give an account for anything in his experience. To make sense of any fact of its origin or design without having a Christian worldview.


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