The Toothpaste Proof of God’s Existence

Notes from Greg L. Bahnsen’s lecture series, What Me? Defend the Faith?

Just a reminder that the Bible throughout styles those who do not believe in God and who refuse to live in terms of it as fools, not in a name calling sense, but one who is morally obstinate. Knowing that unbelievers are fools, listen to what Proverbs 26:4-5 tells us about answering fools.

This looks like a contradiction. How can this possibly be? The Bible gives us two strategies of answering the fool and we can use both of them. Notice firstly, we are told to not answer the fool according to his folly. Why? Because if you buy into foolish philosophy of the unbeliever, you will end up being a fool too. If you try to reason in the way that unbelievers do, in the end they will win the argument because you have already lost it. By giving into their presuppositions you have already lost. Do not give up your ultimate commitments about your metaphysics, epistemology and ethics. Don’t try to agree with them on those and try to bring them back to the Christian faith.

There is another strategy which is not contrary to what we are told, because there is a different explanation for why we do now answer a fool according to his folly. We do answer a fool according to his folly lest the fool be wise in his own eyes. The unbeliever would think that he is justified in not believing in God and that his worldview is just fine.

If what the unbeliever says is true, they cannot make sense out of anything given their view of the world. I’m going to illustrate this in terms of the Toothpaste Proof of God’s Existence. I’m trying to show you that you can take the most mundane thing and demonstrate to the unbeliever that they must believe in God. Why is that? You pick up the toothpaste tube and you squeeze it. What do you expect to happen? You expect toothpaste to squirt out, but how does the unbeliever expect toothpaste to come out?

Christian: Why do you expect toothpaste to come out?
Unbeliever: Because of past experience. I’ve had plenty of experiences of when I squeezed the toothpaste tube, toothpaste would come out.

Is it true that we expect the toothpaste to come out simply because of experience of it in the past? In a second or two, I am expecting toothpaste to squirt out of this tube. I am asking why you believe that the future will have this kind of event. The unbeliever will answer “because in the past when I squeezed the tube, toothpaste came out.” At this point the case is that because in the past it happened this way and therefore, we know it will happen this way in the future. Does anyone see a gap in this reasoning? The gap is “how do we get from past experience to future experience?” Why should we expect what will happen right now will be like the way it was in the past?

We must answer that we have a reason for believing that the toothpaste will come out of the tube and that unbelievers don’t. The unbeliever will say,”of course I do, it has happened in the past.” Now this is the crucial apologetical move. You must say, “So you must believe that this just doesn’t happen in the past, you must also believe that the future will be like the past. You must believe that there is uniformity in the natural world.” The unbeliever in order to brush is teeth must believe something about the nature of reality, which is that there is continuity about the way things happen in the past and the future. This is a huge claim. No one has experienced everything about the nature of reality, so he cannot make this kind of universal judgment. The unbeliever hasn’t experienced the future, so he can’t make any judgment about it.

Unbelievers operate in the manner of believing the future will be like the past, because they know the God who controls history. You cannot count of the uniformity of nature without God, because everything would happen by chance. I’d like to respond to two responses to the Toothpaste Proof of God’s existence. The proof to rehearse it to you is you compare worldviews and ask which one can make sense out of brushing our teeth– the future being like the past. It fits into the Christian worldview but not the atheistic worldview.

Response 1: We know the future will be like the past, because it has always been like that in the past.

Reply 1: In the past the future has always been like the past. Past futures have resembled past past’s, so that now the future will be like the past. Will our present futures be like our present pasts, if in our past the future has always been like the past? The error in the response in begging the question. The issue has to do with the future will resemble things that have happened in the past. The answer that we have been given is that “in the past the future has always been like the past.” This doesn’t answer the question because we want to know if the future will be like the past. Christians have every reason to expect so, because God created the world orderly.

Response 2: We can’t be sure, but very probably the future will be like the past.

Reply 2: This is missing the point. We are not talking about certainty regarding the future being like the past. We are asking whether they even have any basis for thinking it will probably be like the past.

The point that needs to be made to the unbeliever is that the unbeliever assumes AND insists upon the uniformity of nature. If your next door neighbor atheist were to squeeze his toothpaste and it wouldn’t come out, he would think of another explanation. Perhaps the toothpaste is hardened or the hole is blocked. The atheist works with the hypothesis that assumes uniformity.


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