Sermon | How Do You Know That God Exists?

 

HOW DO YOU KNOW THAT GOD EXISTS?
Apologetics 2025
By Andy Manning

INTRODUCTION

Today we are going to start a new sermon series on apologetics.  

What is apologetics?  

1 Peter 3:15 “but in your hearts regard Christ the Lord as holy, ready at any time to give a defense to anyone who asks you for a reason for the hope that is in you.”  

You need to be ready to defend your beliefs.

The Greek word for “defense” is “apologia.”  It was originally used as a speech of defense.  In ancient Greece it referred to a defense made in a courtroom.  After the accusation, the defendant was allowed to refute the charges with a defense.  So apologetics has nothing to do with making an apology.  Instead means defending the Christian faith.  (Kenneth Boa, “What is Apologetics?”, If God Made the Universe, Who Made God? 1)

Apologetics is giving answers to the questions that nonbelievers have about God – questions like…

• How do you know that God exists?
• Why do you trust the bible?
• What’s wrong with abortion?
• Doesn’t science disprove the Bible?  
• If God exists, why is there so much evil and suffering in the world?  

The Bible says you need to always be ready to answer questions like these.  

In other words, it is not enough to know what you believe; you need to know why you believe it.  

Today we are going to tackle the biggest question of all.  How do you know that God exists? 

If somebody asked you, “Why do you believe in God?”  What would you say?  

There are three main arguments for the existence of God.  

THREE ARGUMENTS FOR THE EXISTENCE OF GOD

1) The Cosmological Argument.

The simplest way to state the cosmological argument is this:  something cannot come from nothing.

When you look around, you see something rather than nothing.  Where did it all come from?  Something had to cause everything to come into existence?  In other words, God.  

A more in-depth explanation of the cosmological argument can be presented with the following syllogism:  

• Whatever begins to exist has a cause.
• The universe began to exist.
• Therefore, the universe has a cause.  

If it can be demonstrated that the first two premises are true, then the conclusion is also true.  

Is the first premise true – Whatever begins to exist has a cause?

Have you ever seen anything come from nothing?  Have you ever seen something just pop into existence?  No one has.  Everyday experience and scientific evidence confirm that if something begins to exist, it must have a cause.  Something that doesn’t exist can’t do anything.  

A science professor was walking in the forest with one of his students.  Along the way the student said, “Hey, look, there’s a little glass sphere on the ground.”  And so they picked it up and examined it.  The professor said, “I wonder where that came from?”  They looked around but didn’t see anybody.  The student said, “Yeah, I wonder.”  Then, with a little twinkle in his eye, he said to his science professor, “I wonder, if it were ten times bigger, would we know where it came from then?  And the professor said, “Well, it had to come from somewhere; I don’t think it just showed up.”  The student responded, “Yeah, I agree with that.  But what if it were, like, a hundred times bigger than it is?”  “Well,” said the professor after a moment, “all the more reason to know it had to come from somewhere.”  The student asked, “So let me ask you this.  What if it were, like, a million times bigger?”  The professor finally picked up the student’s drift and said with a chuckle, “Well, then it would have gotten here on its own.”  Nothing got here on its own.  Nothing just pops into existence.  There are no examples of this in nature.  Everything that begins to exist has a cause.  

Notice I said everything that “begins” to exist has a cause.  That’s important.  If I just said, “Everything that exists has a cause,” that would mean that God would need to have a cause.  Only things that begin to exist need a cause; God is eternal, so He needs no cause.  

Is the second premise true – The universe began to exist?

It used to be held that the universe was eternal.  But several recent scientific discoveries have proven that the universe had a beginning.  

The second law of thermodynamics or the Law of Entropy (developed in the mid-19th century) indicates that the universe is slowly running out of usable energy.  If the universe had been here forever, it would have run out of energy by now.  Therefore, the universe must have had a definite beginning.

In 1929 Edwin Hubble looked through his telescope and discovered that the universe was expanding, taking galaxies farther and farther away from each other.  If everything is expanding, then if you go back in time the galaxies would be closer together.  If you go back far enough, the universe shrinks into nothing and disappears.  In other words, he was able to see with his own eyes that the universe had a beginning.  

The vast majority of scientists are convinced that the universe was created fifteen billion years ago in a huge explosion called the Big Bang.

Stephen Hawking (Theoretical physicist and cosmologist) wrote, “Almost everyone now believes that the universe, and time itself, had a beginning at the Big Bang.”  (Hawking and Penrose, The Nature of Time and Space, p. 20)

Therefore, the second premise is true.  The universe began to exist. 

If the two premises are true, then the conclusion is true.  The universe has a cause.  

What could cause the creation of the universe?  

Before you answer that question, there’s something you need to know.  The universe includes time, space, and matter.  Before the universe was created there was no time, no space, and no matter.  Before the Big Bang there was nothing, and the Bang, there was something.  

Therefore, whatever caused the Big Bang would have to be…

• Spaceless
• Timeless
• Immaterial
• Powerful
• Intelligent
• Uncaused
• In other words, God.   

To put it differently, before the universe there was no such thing as nature.  The creation of the universe of the universe was the creation of nature.  Therefore, something outside of nature, or supernatural, had to create the universe.  In other words, God.

Scientist Francis Collins put it this way in his book The Language of God:  “We have this very solid conclusion that the universe had an origin, the Big Bang.  Fifteen billion years ago, the universe began with an unimaginably bright flash of energy from an infinitesimally small point.  That implies that before that, there was nothing.  I can’t imagine how nature, in this case the universe, could have created itself.  And the very fact that the universe had a beginning implies that someone was able to begin it.  And it seems to me that had to be outside of nature.”  

The Bible, of course, tells us where the universe came from.  

Genesis 1:1 “In the beginning God created the heavens and the earth.”

The first argument for the existence of God is the cosmological argument.  To put it simply, something cannot come from nothing.  There’s clearly something, so where did it come from?  The best explanation is God.  

2) The Teleological Argument.

The teleological argument is also called the intelligent design argument, or the fine-tuning argument. 

The simplest way to state it is like this:  Design is proof of a designer.   

When you look at the universe, or our planet, or even life itself, you see obvious signs of design.  Design requires a designer.  What kind of being could design the universe?  It would have to be someone all-knowing and all-powerful.  In other words, God.  

What do I mean that the universe shows obvious signs of design?

Scientists have found that the universe appears to have been designed intentionally to allow for life to exist.  

The structure of the universe is determined by a series of fundamental or universal constants – the speed of light, the gravitational constant, the strength of the weak and strong nuclear forces, etc.  If any of these numbers were altered by even a hairsbreadth, life would not be possible.  Let me give you two examples.

For example, the force of gravity is determined by the gravitational constant.  If the gravitational constant were altered by just 1 part in 10 to the 60th, life would not be possible.  10 to the 60th is 1 with 60 zeros after it.  To give you an idea of the size of that number, you have 10 to the 14th cells in your body.  From the beginning of the universe until now, 10 to the 20th seconds have ticked since the beginning of the universe.  But we’re talking about 10 to the 60th.  Imagine a dial (like you might have on your kitchen oven) divided into 10 to the 60th increments.  If the gravitational constant were altered by just one increment, life in the universe would not be possible (the universe would expand too rapidly or too slowly).

The question is why is the gravitational constant just right for life to exist?  Chance?  No.  The odds are impossible.

A second example is the cosmological constant, which determines the expansion rate of the universe.  If the cosmological constant were altered by one part in 10 to the 120th power, life could not exist (the universe would expand too rapidly or too slowly).  Remember, when we were talking about the gravitational constant, it was 1 part in 10 to the 60th.  Now we’re talking about 1 part in 10 to the 120th.  That’s one part in a trillion, trillion, trillion, trillion, trillion, trillion, trillion, trillion, trillion, trillion. 

Against, why is the cosmological constant set just right for life to be possible?  The odds are infinitesimal.  

Theologian Tim Keller wrote, “The probability of this perfect calibration happening by chance is so tiny as to be statistically negligible.”  (The Reason for God, 134.)

But that’s just two constants.  According to Astrophysicist Hugh Ross, there are at least 35 universal constants like this in the universe that had to be set perfectly, down to a fraction of a fraction, for life to be possible.  

In other words, our universe only supports life because these numbers are finely tuned and balanced on a razor’s edge.   

What is the best explanation?  Why is the universe finely tuned for life?

The smartest scientists say the fine-tuning of the universe points to design and not chance.  

Stephen Hawking said, “The odds against a universe like ours emerging out of something like the Big Bang are enormous.  I think there are clearly religious implications.”  (Quoted in Tim Keller’s The Reason for God, 134.)

Stephen Hawking also said, “It would be very difficult to explain why the universe would have begun in just this way expect as the act of a God who intended to create beings like us.” (Quoted in Tim Keller’s The Reason for God, 134.)

This has been called the “Anthropic Principle,” which is the idea that the universe was created specifically for human beings.  

Someone might object, the odds may be crazy, but there is a chance.  That reminds of the scene in the movie Dumb and Dumber in which Jim Carey’s character, Lloyd – the ultimate idiot, asks this beautiful woman, “What do you think the chances are of a guy like me and a girl like you ending up together?”  She replied, “Not good.”  He said, “You mean not good like one out of a hundred?”  She said, “I’d say more like one out of a million.”  Then Lloyd says, “So you’re telling me there’s a chance.  Yeah!”   

What if you were walking through the forest and you came upon an abandoned cabin.  As you get closer, you notice something very strange.  Above the door there is a sign with your name on it.  When you go inside, you notice that the temperature is exactly how you like it.  The refrigerator and the pantry have all your favorite foods.  And your favorite movie is playing on the TV.  On the table there’s a stack of your favorite board games and DVDs.  The closet is filled with clothing that is just your size.  Would you conclude that the cabin and everything about it was there by chance?  Of course not.  That’s not reasonable.  It was obviously designed with you in mind.  

When you look at the universe, you see obvious signs of design, and design is proof of a designer.  

What kind of a designer could create a universe?  God.  

3) The Moral Law Argument.

The simplest way to state the moral law argument is this:  The moral law in our hearts proves the existence of a moral law giver.  

Let’s look at it in the form of a syllogism:

• Every law has a law giver.
• There is a Moral Law.
• Therefore, there is a Moral Law giver.  

Romans 2:15 “They show that the work of the law is written on their hearts. Their consciences confirm this. Their competing thoughts either accuse or even excuse them”

The Bible says that God has written His moral law on the human heart.  In other words, all people have been given a sense of right and wrong.  This is obvious.  Everyone knows that love is better than hate, and courage is better than cowardice.  Everyone knows that murder is bad, and gratitude is good.  Some people call this moral intuition conscience, or natural law, or nature’s law.  

In other words, it is obvious that there are moral absolutes.  There are moral obligations that are binding on all people, at all times, in all places.  And if there are moral absolutes, then there must be a moral law giver.  In other words, God.  

Doesn’t morality differ from culture to culture?

Dave Sterrett, in the Apologetics Study Bible for Students, wrote, “While it is true that moral codes differ from one culture to the next, the differences are minor.  The deep principles (prohibitions against murder, theft, lying, etc., plus the positive values of honesty, fidelity, and courage) are universal.”

In his book The Abolition of Man, C.S. Lewis lists various universally recognized moral laws and virtues – impartial justice, truthfulness, kindness, mercy, marital fidelity, respect for human life.  They have been regarded as true for all from ancient Babylon and Greece to Native America, from Jews and Christians to Hindus and Confucians.

Dr. Martin Luther King, Jr. pointed to the existence of objective morality to explain the evil of racism:  “I’m here to say to you this morning that some things are right and some things are wrong.  Eternally so, absolutely so.  It’s wrong to hate.  It always has been wrong and it always will be wrong!  It’s wrong in America, it’s wrong in Germany, it’s wrong in Russia, it’s wrong in China.  It was wrong in 2000 BC, and it’s wrong in 1954 AD.  It always has been wrong… Some things in this universe are absolute.  The God of the universe has made it so.  And so long as we adopt this relative attitude toward right and wrong, we’re revolting against the very laws of God himself.”  (From “Rediscovering Lost Values,” a speech delivered in Detroit, Feb 28, 1954.)

Some people of course believe that morality is relative.  Relativism is the most widely held moral view in our culture.  The claim of moral relativism is that there are no moral absolutes; that morality is decided by individuals and cultures.  Morality is not objective and absolute; it’s a matter of opinion, of preference, of taste.  What’s wrong for you may not be wrong for me.  

But nobody truly believes in moral relativism.  There are a few ways to prove this.  

First, everyone demands to be treated fairly.  In other words, if someone says that there are no moral absolutes, then just treat them unfairly.  They may claim it is not objectively wrong to lie, but if their spouse or a politician lied to them, they would vehemently protest.  They may claim that it is not objectively wrong to steal, but if you stole something from them they would cry foul.  

Philosopher J.P. Moreland tells of a time he spoke with a student tin a dorm room about relativism.  The student basically said what was true for him was true for him and what was true for Moreland was no less legitimate even though it might be different.  Moreland thanked the student for his time, picked up the student’s stereo and began to leave.  The student, predictably, protested.  Moreland said he agreed with the student, that morality was a personal issue, and went on to say he didn’t think stealing was wrong.  It is fine for the student to think stealing is wrong, but he shouldn’t push his morality on those who think it is okay.

Second, everyone is passionate about something.  To prove they do believe in moral absolutes, just relativize their passion.  Just say, “Okay.  If morality is relative, then it wouldn’t be wrong for Christians to outlaw atheism; there would be nothing wrong with gay-bashing, or racism, or ethnic cleansing, or torturing animals, or polluting the environment, or outlawing abortion.  Right?”  They wouldn’t agree to that.  

Doug Powell said explained how to prove that your friend does indeed believe in moral absolutes.  “For example, if they deeply believe in animal rights and are heavily involved in PETA, tell them how you are trying to find a new shampoo and just tested out a couple of brands by rubbing it into the eyes of your dog to see whether was an adverse reaction.”

Nobody truly believes in moral relativism.  It is always wrong to torture babies and to rape women – in every culture, in every society, in every generation.  

Where does this moral law come from?  Some might say, “It comes from evolution.  Over time humans developed a moral sense to ensure the survival of the human race.”  But if that’s the case, then you are still left with the same problem.  If morality is just a biological instinct, then it’s not real.  Torturing babies is not actually wrong.  Raping women is not actually wrong.  Hitler is not actually evil.  But nobody believes that.  

Again, where does this moral law come from?  Where do moral absolutes come from?  There has to be a moral law giver.  

C.S. Lewis is one of the greatest Christian thinkers of all time, and it was the moral law argument that led to his conversion.  He wrote, “As an atheist my argument against God was that the universe seemed so cruel and unjust.  But how had I got this idea of just and unjust?  A man does not call a line crooked unless he has some idea of a straight line.  What was I comparing this universe with when I called it unjust?”

Everyone has an innate sense of justice and injustice.  We know it when we see it.  Where did that come from?  The moral law in our hearts proves the existence of a moral law giver.   

CONCLUSION

So, if someone asked you, “Why do you believe in God?” you have three simple answers:  

Something cannot come from nothing.

Design is proof of a designer.

The moral law in our hearts proves the existence of a moral law giver.  

A 2022 Gallup survey found that 81% of Americans profess belief in God.  That’s an all-time low, but it’s still 81%.  Why do so many people believe in something they can’t see.  81% don’t believe in Santa Claus.  81% don’t believe in the Tooth Fairy.  81% don’t believe in aliens.  Why do so many people believe in God?   

Romans 1:18-20 18 For God’s wrath is revealed from heaven against all godlessness and unrighteousness of people who by their unrighteousness suppress the truth, 19 since what can be known about God is evident among them, because God has shown it to them. 20 For his invisible attributes, that is, his eternal power and divine nature, have been clearly seen since the creation of the world, being understood through what he has made. As a result, people are without excuse. 

This passage makes two important points.  

First, it says that God has made His existence obvious.  He has left hints all over the universe that point to Him.  When you take an honest look at all the evidence, it takes more faith to be an atheist than it does to believe in God.  This is why most people believe in God.  

Second, it says that some people suppress the truth.  The reason that some people don’t believe is not because they are unconvinced by the evidence, it is because they don’t want to believe.  They don’t want God to exist.  Because if God exists, then they accountable to Him.  They don’t want to give lose their autonomy; they don’t want to give up their sin.

Here’s the obvious truth.  God exists, and you are accountable to Him.  One day you will have to stand before God to be judged for everything you have done.  The bad news is that you are a sinner, and you deserve eternal punishment.  The good news is that God loves you, and He has provided a way for you to be forgiven and go to heaven.  He sent His Son, Jesus Christ, to die for your sins; He was punished in your place, and He rose again.  The Bible says God will forgive you and give you eternal life if you do three things – ABC.  

• Admit you are a sinner in need of a Savior.
• Believe that Jesus is the Savior who died for your sins and rose again.  
• Call on Jesus to be your Savior and Lord, repenting of your sins.