For those of you who would like to explore what some of the great thinkers of history wrote about the existence of God, this article is for you!  It’s fairly straight forward, clear, and representative of the history of Christian thought about believing in God.

The Unmoved Mover (First Proof, Aquinas, 1225-1274)

Here is the logic behind the argument:

1. We see in the world that things are in motion.
2. Anything that is in motion is being moved by something else.  It cannot move itself, even if it has the potential to move.  This other thing causes it to move.
3. But this other thing is also being moved by something else, and this something else is being moved by something else, and so on.
4. This cannot go on for infinity.
5. All causes today are instruments of the first cause.
6. Therefore, there must be an Unmoved Mover, the First Cause of all motion.  This “First Cause” is God.

Here’s the bottom line.  Aquinas points to the existence of the whole cosmos and asks for a cause that is sufficient enough to produce the universe we have.  An infinite chain of events (infinite regress) is absurd: it cannot go back forever.  There needs to be a First Cause, whom we call God.  In other words, can you explain how you came into this world without mentioning God?  My parents made me…my grandparents made them…all the way back to our first parents…but who made them?  And who made the elements that made the elements from which they were made?  Who got life going in the first place?  The First Cause of all motion and life is God.

The Necessary Being (Third Proof, Aquinas, 1225-1274)

Here’s the logic behind this second proof.

1. A contingent being depends upon something else for existence (contingent beings include nature, people, animals, objects, and all other created matter).
2. A Necessary Being does not depend upon anything else for its existence.  A Necessary Being doesn’t need anything or anyone.
3. There must be a Necessary Being, because not everything can be contingent, because then nothing in the world would exist (for there would be nothing to cause or sustain its existence).
4. The Necessary Being is responsible for creating and sustaining everything, though nothing sustains the Necessary Being.
5. We call this Necessary Being God.

In plain language, we all can’t be acorns, at least one needs to be an oak tree.  If I see a field full of acorns, then I know that there must be an oak tree somewhere.  For the acorns are contingent to the oak tree, they depend on there being an oak tree and they would not exist were it not for an oak tree.  This illustration is insufficient, for even this oak tree came from an acorn.  God, however, is the First Cause, the only Necessary being through which both the tree and the seed exist, the tree first and then the seed from it.

The Sufficient Reason (Leibniz, 1646-1716)

Let me walk you through the logic of this third argument.

1. There is a sufficient reason for the universe.
2. Why is there something rather than nothing?
3. Nothing happens without a sufficient reason.
4. The reason cannot be found within any single thing in this universe, for they are contingent.
5. The reason must be found outside the universe, in a Being whose sufficient reason is self-contained.  He is His own reason.

Here’s what Leibniz is saying.  What is the probability of you getting up from your chair and building a universe versus you staying in your seat and doing nothing?  Nothing is more probable; creating something is less probable and needs a sufficient reason.  God is the sufficient reason for the existence of the universe.

The Cause of It All (Kalām Cosmological Argument)

This is a good argument to think about.

1. Whatever begins to exist has a cause.
2. The universe began to exist.  The absurdity of infinity points to this (if the universe forever existed, then we would never be able to get to the present moment in time, for one could just infinitely back up time’s starting point).  The Big Bang points to this (the universe has a definite starting point and has not existed forever).
3. Therefore, the universe has a cause.
4. And we call this Cause God.

The Watchmaker (William Paley, 1804)

Someone has put things together to accomplish a goal (this is a teleological argument).  Look at the design of the world’s systems.  What is the likelihood that all things would come into order like they did?  Here’s the logic.

1. Let’s say you are walking through the woods.
2. If your toe hits a rock, you might assume that the rock has always been there.
3. But what if your toe hits a watch on the forest floor?
   1. You would not say that the watch had been there forever.
   2. You would not say this even if you had never seen a watch before.
   3. You would not say this even if the watch did not work.
   4. You would not say that this watch was reproduced from another watch that was on the forest floor, and it from another on the forest floor, and so on, because the design would be left unaccounted for.
   5. You would know that it was left there by an intelligent, purposeful creator.
4. Look at our world.  Our world-maker, just like the watchmaker, was an intelligent, purposeful Creator.

Now, let’s say you are walking in the wood and your toe hits John Smith, lying on the forest floor.  Would you assume he has been there for eternity, or that he was left by an intelligent agent?

The Moral Law Giver (C. S. Lewis)

1. People everywhere seem to have a good sense of right and wrong.  It is wrong to exterminate humans in death camps or fly planes into buildings, while it is right to help an old woman or orphan in need.
2. This sense of right and wrong presupposes a moral law (there needs first to be a moral law, something that tells us what things are right and what things are wrong).
3. Some say that the moral law is taught to us by culture.  But that does not mean that society made it up.  It may teach us the moral law, but it did not make it up.  For, society also teaches us mathematics, but that doesn’t mean that a particular society made up math; rather, math is a discipline of right and wrong, no matter where you are!
4. Some say the moral law is given to us by nature (evolution).  But moral law is not like nature.  For nature describes our behavior (tells us what is).  In contrast, the moral law prescribes what is right and wrong (what we ought to do).  Since it prescribes what we ought to do, where does this obligation come from? (Because you cannot get an “ought” from and “is.”)
5. We would say that God is the Moral Law Giver.
6. Therefore, since there is a Moral Law Giver, then we can know what the moral law is (what we ought to do).  And since we know the moral law, then we can know what good is.  And since we know what good is, we can know what evil is.

The chain:        Moral Law Giver —— Moral Law —— Good —— Evil

The Creator (a biblical argument)

Do you know the expression from the 1600’s, “The proof of the pudding is in the eating,” expressed today as, “The proof’s in the pudd’in”?  This is an expression that tells us that the results are what count.  Here’s the logic behind it.

1. We do not need to see or sense something for it to be real (like God).
2. Perceiving the results of a being or a thing points toward its existence.
3. Since creation cannot exist without a creating agent, creation is the result that points to a Creator.

Here’s one way of putting this argument: do you need to see my parents in order to know that they are real?  Or does seeing the results (their children) suffice?  It says in the Bible that humans are able to see the results of God and that these results should suffice for proof.  There are results in nature that pour forth speech and knowledge concerning their Creator (Psalm 19:1-4).  The results are in the world of God’s invisible qualities, his eternal power and divine nature, being clearly seen and understood from what has been made (Romans 1:20).  Therefore, with these results, the existence of God is painfully clear, and humans are without excuse (again, Romans 1:20).