Evidence for God’s Existence

Dr. Gregory E. Ganssle
Department of Philosophy
Talbot School of Theology

You Cannot Prove God’s Existence

Ever since Immanuel Kant wrote his Critique of Pure Reason, it has been common for thinking people to insist that it is impossible to prove the existence of God. In fact, this claim has been elevated to the level of dogma in American intellectual culture. The reason I know this is considered unquestionable dogma is the reaction I get when I call it into question. When someone says “You cannot prove the existence of God.” I want to ask “How do you know? You just met me! How do you know what I can do?”

What do most people mean when they recite this claim? Most people mean that I cannot provide a philosophical argument for the existence of God which will convince all thinking people. It is impossible, so the story goes, to provide an argument which will compel assent. If my argument will not convince the most ardent atheist, I have not proven God’s existence. Since I cannot convince such an atheist to believe, my arguments do not count as proof. If they do not count as proof, what good are they?

I agree that I cannot provide an argument that will convince all thinking people. But what does this tell me? Does this tell me anything about God? No. This tells me more about the nature of proof than it does about whether God exists. I cannot provide an argument which will convince everyone, without a possibility of doubt, that God exists. That is no problem. You see, I cannot provide an argument for any interesting philosophical conclusion which will be accepted by everyone without possibility of doubt.

I cannot prove beyond the possibility of doubt — in a way that will convince all philosophers that the Rocky Mountains are really here as a mind-independent object. I cannot prove that the entire universe did not pop into existence five minutes ago and that all of our apparent memories are not illusions. I cannot prove that the other people you see on campus have minds. Perhaps they are very clever robots.

There are few interesting philosophical conclusions that can be proven beyond the possibility of doubt. So, the fact that arguments for the existence of God do not produce mathematical certainty does not by itself weaken the case for God’s existence. It simply places the question of God’s existence in the same category as other questions such as that of the existence of the external, mind-independent world and the question of how we know other people have minds.

Does this mean that arguments for the existence of God are useless? Not at all. Sure, I cannot provide an argument which will convince all thinking people but this does not mean I don’t have good reason to believe in God. It may turn out that some of my reasons for believing in God may be persuasive to you. Even if you aren’t persuaded to believe that God exists, my arguments may not be useless. It is reasonable to believe that the mountains are real and our memories are generally reliable and that other minds exist. It is reasonable to believe these things even though they cannot be proven. Maybe some argument for God’s existence will persuade you that belief in God is reasonable.

So how can we know that God exists? Instead of looking for undoubtable conclusions, we weigh evidence and consider alternatives. Which alternative best fits the evidence? We will choose one alternative or another. There is no neutral ground.

Where Can we Find Information about God?

When you get to thinking about it, it seems that there are only two basic sources of information about God, if such a being exists.

They are the following:

  1. We can, first, infer what might be true about God from what we observe in the universe. We look at the physical universe, human nature and culture and we observe things which may be clues to the existence or nature of the supernatural.
  2. Second, God may have entered the Universe and told us true things about himself, morality, meaning and how to have a relationship with him. This is called Revelation.

Let me explain each of these. One year my wife and I drove from Los Angeles to Rhode Island. It took a long time. The country is pretty big. From this observation it makes sense to think that if there is some person or being who is responsible for making the physical universe, this being has a lot more power than we do. Now this is a rather simplistic example. Another observation we can make is that every culture we know anything about has a deep sense that certain things are morally permissible and certain things are morally prohibited. This leads us to infer that if there is some supernatural being responsible for human nature, that being is personal. He has a moral aspect to his nature.

The second source of information is that God may have taken the initiative and stepped into the universe to reveal himself. He may tell us true things about his nature and purposes and about human meaning and morality.

Christianity holds that both of these are good sources of information. We have clues to God’s existence which can be observed and God has entered the physical universe through the life and teaching of Jesus of Nazareth in History and told us about himself.

Now in this article I am concentrating on the first source. Can we know anything about God from what we observe? Are there good reasons to believe in God based on these observations? I think there are.

Reasons to Believe in God

I want to pick up two observations which I think give us good reason to think there is a God. First, the existence of the universe is better explained by the existence of God. Second, the existence of objective moral values is better explained by the existence of God.

Reason One: The Existence of the Universe is Better Explained by The Existence of God.
I will begin by laying out the argument:

There are things which come into existence.
Everything which comes into existence is caused to exist by something else.
There cannot be an infinite series of past causes.
Therefore, there exists a first cause which did not come into existence. In other words, the first cause always existed.

Let us look at each of the steps in the argument:

Premise 1. “There are things which come into existence.”
Many things have come into existence. This article is coming into existence as I write it. You came into existence and so did I. This premise is not controversial.

Premise 2. “Everything which comes into existence is caused to exist by something else.”
It is obvious that nothing can cause itself to come into existence. Anything that causes itself to come into existence has to exist before it exists. This is impossible. Perhaps something can come into existence from Nothing without any cause whatsoever. Can a thing just pop into existence with absolutely no cause? This also does not seem reasonable.

When my children were young, they would sometimes draw on the walls.  If I walked into the dining room and saw a picture of Pinky and the Brain drawn on the wall in Permanent Magic Marker I would have asked “Where did this picture come from?” My daughter Elizabeth might have said “It came from nothing, Dad. Nothing caused it. It just popped there. I think it is quite strange — don’t you?” Would I have accepted this? No! Things do not come into existence from Nothing without cause. So, we have good reason to think that premise two is true. Everything which comes into existence is caused to exist by something else.

Premise 3. “There cannot be an infinite series of past causes.”
Is the series of past causes infinite? Can the universe have an infinite past? The answer is that it cannot. First, there are philosophical reasons to think the past cannot be infinite. Second, there are scientific reasons which support this view.

Philosophical Reasons
Why can’t the past be infinite? The answer is that it is impossible to complete an infinite series by addition. The series of past events is complete. Think of this mathematical fact. Why is it impossible to count to infinity? It is impossible because, no matter how long you count, you will always be at a finite number. It is impossible to complete an actual infinite by successive addition.

The past is complete. This claim means that the entire series of past events ends now. It ends today. Tomorrow is not part of the series of past events. The series of past events does not extend into the future. It is complete at the present. If it is impossible to complete an infinite series by successive addition (as it is impossible to count to infinity) the past cannot be infinite. If the past is finite, that is, if it had a beginning, then the universe had a beginning. We have strong philosophical reason to reject the claim that the universe has always existed.

Scientific Reasons
I will not develop these. Rather, I will simply point them out.

Big Bang theory does not prove that the universe had a beginning, but it supports this claim.
The second law of thermodynamics does not prove that the universe had a beginning but it also supports this claim.
We can see that we have good philosophical and Scientific reasons to reject the idea that the Universe has always existed.

About the Universe, there are only three alternatives:
1. The universe has always existed. It has an infinite past.
2. The universe was popped into existence from nothing with absolutely no cause.
3. The universe was caused to exist by something outside it.

We have strong reason to reject the first two alternatives.

Alternative Three is the most reasonable. There was a first cause. This cause existed eternally. It initiated the big bang and created the universe. Now what can we know about this cause? Why think the cause is God? I will briefly sketch a few implications.

First, the first cause is not a part of the space-time physical universe because it caused the space time universe to begin. Therefore, it is outside of space and time. It is not physical. Second, it has a great deal of power. Third, it is a personal agent. This means it is not an inert force but it must have aspects of person hood; namely, that it wills. How do we know this? This is because it is the best answer to the question of why the Big Bang happened when it did. Why not sooner? Why not later? All of the conditions for producing the Big Bang existed from eternity. The only kind of cause we know of that can initiate an effect when all of the conditions are already present is the will of a personal agent.

I have not argued that it is logically impossible that the universe popped into existence from nothing without cause. I have argued that it is more reasonable to hold that it has a cause and that this cause is a non-physical personal agent — God.

So, it seems that the first argument is fairly strong. The existence of the universe is better explained by the existence of God.

Reason Two: The Existence of Objective Moral Obligations is Better Explained by the Existence of God.
People experience a sense of morality that leads them to hold strongly that certain things are right or wrong for all people in all cultures. For example, it is wrong to torture another person just for fun. It is wrong for me today. It is wrong for a citizen of the Philippines and it was wrong for someone living in 500 BC. If it is true that it is wrong to torture another person just for fun, then our moral sense picks up something real and objective about morality.

Some philosophers have argued that without God there can be no objective morality at all. In fact, I used to argue for this claim myself. I have changed my mind about this point. I think there can be objective moral goods without God. For example, Aristotle believed that there are objective facts concerning what helps human beings flourish. Human flourishing is clearly a moral good. Thus, there can be some objective moral goods without God. It is more difficult to find room for objective moral obligations without God.

What is the difference between a moral good and a moral obligation? A moral good is a state or situation that, morally, is better to have than not.  We might think that it is a better situation, morally, if a person can fulfill some of her potential than if she cannot fulfill any of it. A moral obligation is a duty. If I have a moral obligation to do some action, then I have a duty to perform it. If I refrain from doing the action, I fail at one of my duties, and I am in that sense blameworthy.

What I will argue is that objective moral obligation is better explained by the existence of God than by atheist stories. I will not argue that objective moral obligations are impossible without God. I will argue they are more likely if God exists. If I am correct, objective moral obligations will be evidence for God’s existence.

Before I go any further, I must make it clear that I am not claiming that one must believe in God in order to be moral. I am not claiming that statistically those who believe in God are more moral than those who do not. I am also not claiming that our knowledge of morality depends upon God. This argument is to the effect that objective moral obligations themselves are surprising in a universe without God. They do not fit.

We have different kinds of obligations. Some are prudential, such as “you should prepare for the final exam.” Others have to do with playing a game such as “you cannot move your bishop along the horizontal.” Others are moral. One fact that separates moral obligations from other obligations is that non-moral obligations are actually conditionals. For example, you should prepare for the final exam if you want to do well in the class. You cannot more your bishop along the horizontal if you want to play chess according to the rules.

We can call this kind of obligations conditional obligations. There are two things to observe about conditional conditions. First, if the condition is not fulfilled, the obligation does not hold. Second, it is up to the person involved if she wants to fulfill the condition. So, it is up to you if you want to play chess according to the rules. If you do want to play according to the rules, then you have the obligation not to move the bishop across the horizontal. If you do not care about doing well in the class, you don’t have the obligation to prepare for the final exam. It is up to you if you care.

Moral obligations are not conditional in this way. Suppose you are in a situation in which it would be morally wrong to lie. Someone might want to say that your obligation is conditional. In other words, the moral claim is the following: “If you want to be moral, you must tell the truth in this particular situation.” This sentence is true. If you do not speak the truth, you are not acting morally in that situation. Notice that you are free to reject the condition. You can decide to act in a way that is not moral. If you decide to reject the condition, however, you are not released from the obligation. You may choose to act to fulfill your obligation or not to fulfill it. Either way, the obligation still holds. This observation about moral obligation is a feature of our widely shared concept of moral obligations. It is part of what it means to be under such an obligation.

Part of what makes moral obligations objective is this fact that whether they apply is not up to us. We are not free to refuse to “play the morality game” the way we can refuse to play chess and move the pieces however we want.

There is one more thing to notice about our different kinds of obligations. Conditional obligations are related to conditional purposes. If my purpose is to do well in a class, the obligation to study is binding on me. If my purpose is to play chess according to the rules, the obligation about how I may move my pieces holds. As I said, these conditions are in some sense up to us. Therefore, the purposes are up to us. We can opt in or opt out. Moral obligations seem to be related to purpose as well. If we want to act the way a human being ought to act, we should not lie in a specific situation. The purpose in an unconditional obligation is an unconditional purpose. It is not up to me but it holds.

Given these observations about the nature of obligations, and about moral obligations in particular, we can see that the existence of objective moral obligations makes sense if God is real. They might not be impossible without God, but it is surprising that the universe would develop objective, unconditional purposes for human beings simply by accident.

God, if he exists, is a powerful person who creates the universe (and human beings) for his own reasons. Some of these reasons constitute human purpose. Christianity, for example, specifies that part of God’s purposes in creating us is that we would embody and practice various virtues that reflect his own goodness. In this view, it is no surprise that there are unconditional obligations.

If God does not exist, then, although there is a causal story about how human beings emerged, these causes do not provide reasons or purpose for our existence. Objective moral obligations are surprising on this view.


I have briefly presented two arguments for the existence of God. Of course, there are many other arguments to consider on both sides, and each could be developed in much more detail. I have presented enough, I think, to suggest that it is more reasonable to believe that God exists than that He does not exist.

So, we see that some of the things we observe about the natural world ground a strong inference to the claim that God does exist. This gives us reason to consider with renewed openness the possibility that God has entered the space-time universe and revealed Himself through the person and life and death of Jesus of Nazareth.

I have not claimed to prove with mathematical certainty that God exists. I have, however, provided good reasons to think that He does. If someone wishes to argue successfully that God does not exist, he must first, provide an answer for each of my arguments and second, he must offer arguments that God does not exist. Until He does this, we can conclude that we have good reason to claim that God does exist.

Go Deeper

The Creator Revealed

To explore the Scientific Reasons to believe in God we recommend The Creator Revealed by Dr. Michael Strauss

Does God Exist?

To explore more of the philosophical reasons to believe in God we recommend Does God Exist? by William Lane Craig.

Greg Ganssle has been thinking about the intersection of Christian faith and contemporary scholarship for over thirty years. He began as an undergraduate by skipping his classes and reading C.S. Lewis. After graduating from the University of Maryland in 1978, he worked in campus ministry on a variety of campuses. Hundreds of conversations with students from a wide variety of religious and philosophical perspectives drove him to a sustained self-study program. Eventually it occurred to him that he was reading philosophy. Since he had escaped college without taking a philosophy course, he decided to begin with Philosophy 101 at the age of 25. Within weeks he was hooked. Continuing to juggle his full time campus ministry responsibilities, he earned a Master of Arts in Philosophy from the University of Rhode Island in 1990. He then went full time and earned his doctorate in philosophy from Syracuse University in 1995, where his dissertation on God’s relation to time won a Syracuse University Dissertation Award. In addition to publishing nearly three dozen articles, chapters and reviews, Greg is also the author of Our Deepest Desires: How the Christian Story Fulfills Human Aspirations (IVP, 2017), Thinking about God: First Steps in Philosophy (IVP, 2004) and A Reasonable God: Engaging the New Face of Atheism (Baylor University Press, 2009). Greg was part-time lecturer in the philosophy department at Yale for nine years and a senior fellow at the Rivendell Institute at Yale. Greg has been married to Jeanie since 1985. They have three children, none of whom are philosophers. Although happily married, Greg has a secret crush on Jane Austen.

Grad Resources provides all its articles free of charge.  If you found this article helpful, please consider giving a gift so that we can continue offering resources like these.