Introduction
Are there any compelling reasons to think that God exists? Can we know with good reason that there is a God? If so, what counts as proof? If there is proof, is it scientific proof or philosophical proof? Some of our beliefs are based on reasons that are probably true but not absolutely true. For instance, I believe the chair you're sitting on will not collapse in the next ten seconds. This kind of belief is based on probability and not on philosophical reasoning. The reliability of the persons who put your chair together, along with the materials used to construct it, lead me to conclude that your chair will not collapse. However, I can only conclude that it's probably true, but not absolutely true. In other words, some of my beliefs involve a degree of certainty and don't require absolute certainty.

Other beliefs I hold are absolutely certain and can be shown to be certain philosophically. For example, I believe that I exist. I'm absolutely certain of this. You see, if I try and deny my existence, then I have to exist in order to deny my existence, which ends up proving the very thing I'm denying. Some of our beliefs, therefore, are self-justifying and just make sense.

I suggest that a belief in the existence of God is like both of these kinds of beliefs. Some of our reasons for believing in God involve probability and some of our reasons involve certainty. Together these reasons provide an overwhelming case for believing in God's existence.

I want to show that we can believe God exists, we can have reasons for our belief, and our reasons amount to proof. Specifically, I will demonstrate there are four reasons to believe in the existence of God. While I don't pretend to convince everyone beyond reasonable doubt that God exists, I do hope to show that it is reasonable and rational to believe in the existence of God. Should some remain skeptical I encourage you to consider that doubt does not necessarily weaken the arguments for God's existence. In fact, no amount of doubt will make the question of God's existence disappear. In the final analysis either God exists or he does not. We simply must choose.

The Argument from Cause
Have you ever wondered, "Why is there anything at all?" Most of the things or beings around us do not have to exist. It seems as though they were created and had a beginning. Similarly, it seems that I did not have to exist. If my parents had not met, then I would not exist. Since it seems that everything in the universe did not have to exist, then it looks like everything in the universe is dependent upon something else for its existence. If everything is dependent, then we're saying that everything is contingent; it did not have to exist. We can put the argument this way:

1. Every being that exists is either necessary or contingent.
2. Not every being can be a contingent being.
3. Therefore, there exists a necessary being upon which contingent beings depend.
4. A necessary being on which all contingent beings depend is what we mean by "God."
5. Therefore, God exists.

The next logical question is what caused the things in the universe to come into existence? After all, if there is one thing in the universe that does not depend upon anything else for it's existence, then that thing is self-existent and does not require a cause. Unfortunately, I don't know of anything or anyone that just popped into existence without a cause. So, if everything that is contingent came into existence, then it necessarily has a beginning. We can safely say that whatever has a beginning has a cause. The argument goes like this:

1. Whatever begins to exist has a cause.
2. The universe (and everything in it) began to exist.
3. Therefore, the universe (and everything in it) has a cause.

We know that the first statement is logically true. It's impossible for something to have a beginning in time but have no cause. Things, events, people, just don't pop into existence unexplained. It's also impossible for something to have no beginning in time but still have a cause. If something is caused, then it necessarily had a beginning in time. Things that have a beginning have causes, and things that have causes have beginnings.

The second statement is where the difficulty lies. Not everyone believes the universe had a beginning. That would mean the universe is eternal and needs no explanation. It would also mean that there is an actual infinite amount of time and events that occur in the universe. Now, if there is an actual infinite amount of time that exists (because the universe has always existed), then we could never reach this present moment. Let me explain.

If the universe has always existed, then an infinite number of years have already gone by. But this is inconceivable, because an infinite number of years or events can never "go by" or "occur." How do we know this? Because we are living in the present and experiencing this lecture series as an event. You see, if there are an infinite number of years, then it would take forever to reach this moment in time. But we are here in the present experiencing this lecture series as an event. So it didn't take forever and there are not an infinite number of years.

Consider another analogy. Suppose that before you reached this sentence of this presentation you first had to view the previous sentence and that before you reached that sentence you had to view the previous sentence before it, and so on. Since this presentation has a first sentence, your coming to this sentence entails that you read a finite number of sentences. Now suppose we have an infinite number of sentences before this sentence and you first must read those sentences before coming to this one. When will you get to this sentence? Answer: Never. So if you find yourself reading this sentence, then there must have been a finite number of sentences before this one.

The same holds true for the series of events that make up the total history of the universe. Any event in history (e.g., the birth of my son) can only occur if a finite number of events precede it. If an infinite number of events came before my son's birth, he would never have been born. So, either I am hallucinating that I have a son or a finite number of events occurred prior to his birth. If a finite number of events occurred before my son's birth, then the universe has not always existed, but instead had a beginning. But, this entails that the universe is not eternal. If, therefore, the universe is not eternal, then it had a beginning and this necessitates that the universe is caused. This cause we call God, who is the Uncaused Cause of the universe.

The Argument from Design
Second, the argument from design moves from what looks like design and order in the universe to a master Designer. It's like moving from a work of art to the artist, from a building to its architect, from a song to its composer, or from a book to its author. Could one look at the faces carved into Mount Rushmore and ever believe that they came about by chance or accident? Given an infinite amount of time, wind, rain, and organic materials, it is still hard to believe something like this, tied to history, was randomly formed in this country at this time. Common sense leads us to conclude that people planned and skillfully constructed this grand composition. So too does the universe appear to have intelligence and design built into it. Naturally, this assumes there is a master Architect or intelligent Agent behind the order and design of the universe.

This argument can be formulated in a few ways.

1. Human artifacts (computers, watches, buildings) are products of intelligent design.
2. The universe resembles these human artifacts.
3. Therefore, the universe is (probably) a product of intelligent design.

Or consider another formulation.

1. Living things appear to show signs of intelligent design.
2. Living things that show signs of intelligent design are either a) a product of chance and random processes, or b) intelligent design.
3. Living things are not a product of chance and random processes.
4. Therefore, living things are a product of intelligent design.

You might respond that Darwin showed living things are a product of chance and random processes. However, for Darwin's story to work there must be 3 key elements. First, random distribution of biological variations must be present in living organisms. Second, some variations are better than others in giving species an advantage to survival. Third, variations that survive in species must be hereditary. I'd like to respond to the first of these.

Today, mutation is essentially what is known as random distribution of biological variations. No one questions mutation in species. What is scientifically unsound and vastly improbable is the notion that mutation produces new species from existing species. Why is this so? Every living organism is a complex system of interrelated parts, such as organs. Each organ is a complex system of smaller interrelated parts, such as cells. Each cell is a complex system of even smaller interrelated parts, such as the bacterial flagellum. Now it is a fact that many organs require a combination of complex parts in order to perform their functions and produce a biological advantage to a species. Yet according to Darwinian evolution systems, organs and cells gradually change or mutate over time and not all parts change at the same rate. A commonsense question arises at this point. How could an eye, as a complex system composed of interrelated parts that must operate in concert to be fully functional, gradually change to confer an advantage on the new species if it is only partially functional? You see, an eye could never become what it is in all its complexity and utility if any of its parts randomly changed over time. Should the genetic characteristics of a partially functioning eye be passed on to subsequent generations, the species is far less likely to survive than thrive. The partial evolution of an eye, therefore, would clearly be a disadvantage for survival.

Especially with the advent of genetic engineering, Darwinian evolution is considerably weakened since it depends upon "random variations" rather than carefully planned and engineered products of geneticists in a laboratory. It seems, then, that the random distribution of biological variations is not so "random" after all.

It is significant to note that Darwin's story only applies to living things. Even if it were scientifically demonstrated to be true, Darwin's story does not explain the apparent design in non-living, inorganic things in the universe. This takes us to another form of the Design Argument.

The universe as a whole seems to display immense precision and order such that certain physical constants must be finely tuned in order for the universe to be life-permitting rather than life-prohibiting. Many conditions and values in the physical constants of the universe had to be delicately balanced for our universe to be life-permitting. Should any of these values and conditions be altered by a small fraction, the universe would either not exist at all or be life-prohibiting. In other words, it's extremely improbable that our universe should come into existence with no intelligent Designer behind it to fine-tune all the variables necessary for our universe to be life-permitting. The argument runs like this:

1. The fine-tuning of the universe is due to physical necessity, chance, or design.
2. It is not due to physical necessity or chance.
3. Therefore, it is due to design.
   

The expression "fine-tuning" means that the actual values assumed by the constants and quantities of the physical universe (gravity [electromagnetism], density [proton to electron mass ratio], etc.) are such that small deviations from those values would render the universe life-prohibiting. For example, a change in electromagnetism by one in 10^-40 would be disastrous for the sun, making the existence of other planets in our galaxy impossible. The physical universe does not have to be the way it is; it could have been otherwise. Consider just a few more conditions and values.

Had the rate of expansion of the universe been different (by one part in a million million), no life would have been possible. The material of the observable universe is isotropic (meaning evenly distributed) to an accuracy of 0.1 percent. The balance of matter to antimatter had to be accurate to one part in ten billion for the universe to be as it is. Had the ratio of carbon to oxygen been slightly different, no life would be possible. If the mass of a proton were increased by 0.2 percent, hydrogen would be unstable and life could not have formed. For life to exist and sustain on Earth, the right temperature range must be maintained, which is achieved by a balance of the Earth being just the right distance from the sun, just the right size, maintain the right rotational speed, with the right atmosphere, and contain just the right amount of metals (particularly iron), and just the right radioactive materials (Moreland, Scaling the Secular City, pp. 52ff.).

Now I grant that a million monkeys set in front of a million computers could, given enough time, produce an intelligent, coherent paragraph. But the mathematical probability of that occurring is so small that it takes far more faith to believe in chance and random processes than in intelligent design. A reasonable and rational person could only conclude, upon examining the evidence, that some super Intelligence had something incredible to do with the universe! This super Intelligence we call God.

The Argument from Objective Moral Values
Third, the argument from objective moral values states that some things are really wrong in themselves, not because society says so or because some human choices may be inherently helpful in survival while others are harmful. Abuse, rape, and child torture are really wrong and not just socially unacceptable behaviors. Conversely, honesty, love, and self-sacrifice are values that have no biological explanation and they have never been proven to help humans survive. The argument runs like this:

1. If objective moral values exist, then God exists.
2. Objective moral values exist.
3. Therefore, God exists.
   

It is important to understand that it's not necessary to believe in God in order to live moral lives. What I'm saying is that for objective moral values to exist the best explanation is that there is a moral Lawgiver. Of course, if objective moral values do not exist, then all that we can claim that exists are personal preferences or agreed upon standards of behavior in society. For the atheist then, incest or rape may not be socially advantageous, but these acts cannot be objectively wrong, only relatively wrong. If a person can avoid the negative consequences of committing these acts, then there is nothing really wrong with them. Given enough time and change, society will alter its beliefs and moral values simply become moving targets. But the believer insists that these acts are really wrong and they're wrong because God says so. But of course, this requires God's existence.

The Argument from Miracles
Finally, the argument from miracles suggests that if miracles occur in history, then God exists. If, for example, Jesus really did rise from the dead, then we have a miracle that must be explained. Since alternative explanations fail to account for this event, it seems we have evidence for the existence of God from the miracle of Jesus' resurrection.

Traditionally, there are three historical facts that point to the miracle of the resurrection. First, the tomb where Jesus was buried was found empty. Second, Jesus appeared on several occasions to many after his death. Third, the origin of the Christian Church is evidence for Jesus' resurrection. Let me briefly expand on all three.

It's historically difficult if not impossible to object to the empty tomb of Jesus. If the burial site of Jesus was known, then anyone could have produced the body of Jesus to deny his resurrection. Yet, the tomb was empty. As long as the body of Jesus could have been produced, then it's extremely unlikely that the first disciples would have a following of others. Yet, the Christian Church grew by the thousands within the first few months of Jesus' death, burial, and resurrection because the tomb was empty. Jewish authorities who strongly denied the validity of the Christian message could easily have pointed to the tomb of Jesus if his body remained interred. Yet, the tomb was empty. Not enough time had elapsed between the penning of the first books of the New Testament and the events about which they speak for the resurrection story to become legend or myth. Thus, the accounts written in the New Testament about Jesus' resurrection are historically reliable, because the tomb was empty.

Should someone claim that Jesus' body was stolen to stage a resurrection, it would be impossible to show why these disciples turned from men and women of integrity to charlatans and liars in such a short period. At the time of Jesus' crucifixion and up until the appearances of Jesus (approximately 3 days), the disciples were not psychologically equipped to concoct such a hoax. Instead, they were deeply discouraged, confused, and fearful. The fact that Jesus' followers went from fear to courage, from confusion to clarity, and from discouragement to determination can only be explained if Jesus rose from the dead and appeared to them. Some may object that the disciples were merely hallucinating or psychologically projecting Jesus' appearance. Even if this were true, the empty tomb remains.

Modern scholarship simply has no alternative means for explaining the empty tomb, the resurrection appearances of Jesus, and the rise of the Christian Church. If, therefore, the resurrection of Jesus did occur in history, then we have a divine miracle, and that necessarily requires the existence of God.

Conclusion
We have looked at four arguments demonstrating the existence of God. Together the arguments from causation, design, objective moral values, and miracles show an overwhelming, cumulative case for the existence of God. I began by claiming that we cannot avoid the question of God's existence. Either God is or he is not. You must decide. Life is moving forward and we are all active participants, not distant observers who can choose to remain indifferent. The fact of death is before us all and we must wager. If God does not exist it does not matter how you choose because you've got nothing to lose and nothing to win. If God does exist your only chance of eternal happiness is to believe. If God does exist your only chance of losing eternal happiness is to refuse to believe. As Blaise Pascal put it:

"I should be much more afraid of being mistaken and then finding out that Christianity is true than of being mistaken in believing it to be true….Let us weigh up the gain and the loss involved in calling heads that God exists. Let us assess the two cases: if you win, you win everything: if you lose, you lose nothing. Do not hesitate then: wager that he does exist."

Note: I'm indebted to many for the arguments used here, especially William Lane Craig, Michael J. Behe, Philip Johnson, Peter Kreeft, Gregory E. Ganssle, and J. P. Moreland.