How do we know God exists?
There are several ways by which we know that God exists… and we can prove it. Of course, for those who already believe, and for whom no explanation is necessary, we can know God exists because He has revealed Himself to us (Hebrews 1:1-2).
But what of proofs for His existence? Well…
Now before you balk on that notion, stop and think a moment—getting your prejudices out of the way. You don't balk on belief in gravity or that the earth is round (unless you belong to the Flat Earth Society—yeah, it's real). Until people were able to empirically prove those truths, those things were stated as facts by their discoverers, who had nothing more than logic and right reason for proof. So let's apply a little of that logic and right reason.
Argument from design
Let's view God's existence from design. We can see from nature that it could exist only through the design of a Supreme Architect. Trees "inhale" carbon dioxide and "exhale" oxygen. We inhale oxygen and exhale carbon dioxide. We can't exist without the trees and they can't exist without us. What a logical God!
The food chain teaches us a bit about God's existence. The tiniest microscopic organism is food for the next largest organism, is food for the next largest organism, is food for the next largest organism. And on it goes until it reaches the top of the food chain—us. We eat, digest the food, our bodies evacuate the waste, then the process starts all over again with the tiniest organism feeding on the waste. What a logical God!
"Are you crazy? That stuff is all from evolution! Everybody knows about the fact of evolution. It's science, man."
Whoa! I'm not the one who's crazy. First, evolution isn't a fact; it's a theory. Second, it's a false theory, as it actually violates the very science that is apparently your god.
Evolution contends that order accidentally came from chaos and became the world in nature as we know it. But the third law of thermodynamics tells us the universe is entropy—that all matter is in a constant state of deterioration from order to chaos. If all matter is in a constant state of deterioration, how in the world could chaos evolve into order? You can't have it both ways. Either evolution is right (a theory) or thermodynamics is right (a proven fact).
Argument from conscience
We intuitively know the difference between right and wrong. This is called natural law. It's something that used to be taught in every law school, but the political left has managed to banish natural law from our "scholarly" institutions. The reason the political left banished it is because they fear it; it doesn't comport to their agenda. We have proof of this each time a conservative is nominated to fill a federal bench or the Supreme Court. The first question asked by leftists is whether the nominee adheres to natural law. If he or she admits to adherence, leftists dig in to keep the nominee from being confirmed.
Why do they so fear natural law? Well, thanks to natural law (note that it is universally accepted law; not theory), we intuitively know it is wrong to disobey legitimate authority, wrong to murder (abortion—the reason the left hates natural law), wrong to have sexual encounters with someone not your lifetime mate, wrong to steal, wrong to lie, et cetera. We know all these things intuitively; natural law. So that we have natural law implies a lawgiver. Who else could a lawgiver be but God?
"Wait a minute. The conscience is formed from religious thought in union with the human brain"
What? What debunks your argument that conscience comes from religious teaching is the science of social anthropology and medicine. First, there isn't a neurologist in the world who can tell us what part of the brain the conscience comes from, as the conscience isn't a function of the brain. And, second, anthropologists have discovered tribal communities in remote locations of the world that had a moral code in place when they were discovered that comports to natural law, without the influence of Judo-Christian religions.
Bad man, mad man argument
The argument I'm about to present is one I thought I had originated, but I later found out it was first developed by an obscure saint in the second or third century. I should have known someone had beat me to it, as a 2000 year old Church has already come up with everything that can be thought of.
To present this argument, I'll ask the reader to stipulate a couple of things for the sake of brevity.
The first thing I want you to stipulate is that the Old Testament is ancient Hebrew literature. I'm not claiming it is inspired, infallibly true, or anything else; only that it's ancient Hebrew literature.
The second stipulation I'm asking from you is that Jesus of Nazareth was a real historic person. I'm not saying he's the messiah, God, the son of God or anything else; only that he was a real historic person.
"Got to stop you again! You don't have anything to back up that claim other than the Bible."
Not so! That Jesus was a real historic person is attested to by the writings of men who were contemporaries of Jesus. Specifically, I'm talking about Pliny, Tacitus, Suetonius, and Flavius Josephus. The first three men were pagans and certainly no friends of Jesus. Flavius Josephus was like Paul: he was both a Jew and a Roman citizen, and he was most assuredly not at all sympathetic to Jesus. The writings of these four men, historical scholars tell us, validate the four Gospels, making them historically reliable. So we not only have the testimony of Matthew, Mark, Luke and John, but we also have the writings of Pliny, Tacitus, Suetonius, and Flavius Josephus.
So with these two stipulations made, we can now present our argument.
First, we will consider the Old Testament prophecies of the coming messiah. The Old Testament is filled with such prophecies, particularly in the books of Jeremiah, Isaiah, the Psalms, and even the very first promise in the early part of Genesis. We are still not claiming these prophecies are true, but rather that they are in the Old Testament.
If we were to take all the messianic prophecies and list them in a column, then read all the accounts of the life of Jesus, we find that Jesus fulfilled the prophecies perfectly. But does this prove that Jesus was the messiah? No! Applying logic and reason, we can deduce that Jesus of Nazareth could only be one of three types of persons: a bad man, a mad man, or who he says he is.
Could Jesus have been a bad man? Could a bad man—a criminal—wake up one day and decide that he would fulfill all the messianic prophecies? He could reason that if he could convince the people that he was the messiah by fulfilling the prophecies he would be hailed as their king. He could raise an army and rout the Romans out of Israel, become very wealthy and powerful, have lots of women and material wealth and so on. Could a bad man do that?
Sure he could, but this sort of reasoning breaks down with one prophecy. One of the prophecies says that the messiah would have to die. Now, would a criminal work so hard to fulfill all the prophecies if he knew he would have to die. As someone who has worked in prison apostolate, I've known a lot of criminals. One hallmark of a criminal is that they are selfish and think of themselves before they think of anyone else. So Jesus couldn't have been a criminal. Not a chance!
Could Jesus have been a mad man? Could a mad man wake up one day and say, "What's that, God? You say I'm the messiah and I need to start fulfilling prophecy? Okay, God!" Would or could a mad man do that? Again, that is certainly a possibility, but reason and experience with the insane tells us this won't work. Why? Consistency. A mad man can't remain consistent long enough to pull this off.
A 20th century example is Adolph Hitler. We entered the Second World War in 1941 (Germany declared war against the United States 12-11-41), it was almost three years before we had a significant victory over Germany. Our European enemy had the greatest military and most brilliant generals the world had ever known, but we defeated them anyway. The reason was Hitler's insanity. As long as Hitler listened to his war generals, the Germans won. It was only when Hitler's insanity kicked in and he began listening to his astrologers instead of his generals that we were able to begin to turn the tide of the war to our favor. That's the nature of insanity.
But Jesus was far from insane. The science of psychology only began in 1879, making it a mere 137 years old at this writing. Psychologists agree that if Jesus was nothing else, he was both sane and consistent. While they may not agree with what he taught (or at least the various interpretations of what he taught), they certainly agree he was sane. Therefore, Jesus could not have been a mad man.
Who he says he is
If Jesus couldn't have been a bad man, and if he couldn't have been a mad man, then he must have been who he said he was. And who did he say he was?
He said he was god!
Jesus repeatedly claimed to be God (cf. John 10:24-31, et alia), but my personal favorite is found in John 8:58. Here's what took place…
The Jews said to him, "Are we not right in saying you are a Samaritan and have a demon?" Jesus answered, "I have not a demon; but I honor my Father, and you dishonor me. Yet I do not seek my own glory; there is One who seeks it and he will be the judge. Truly, truly, I say to you, if any one keeps my word, he will never see death." The Jews said to him, "Now we know that you have a demon. Abraham died, as did the prophets; and you say, 'If any one keeps my word, he will never taste death.' Are you greater than our father Abraham, who died? And the prophets died! Who do you claim to be?" Jesus answered, "If I glorify myself, my glory is nothing; it is my Father who glorifies me, of whom you say that he is your God. But you have not known him; I know him. If I said, I do not know him, I should be a liar like you; but I do know him and I keep his word. Your father Abraham rejoiced that he was to see my day; he saw it and was glad." The Jews then said to him, "You are not yet fifty years old, and have you seen Abraham?"Jesus said to them, "Truly, truly, I say to you, before Abraham was, I am." So they took up stones to throw at him; but Jesus hid himself, and went out of the temple. (v. 48-59)
Now Jesus' comment saying that he is "I am" seems pretty innocuous to most of us, and maybe doesn't even make sense to most of us, but it was enough to make the Jews want to kill him. Why?
To get the answer to that we have to go back to the third chapter of Exodus. It is here that God just gave Moses his marching orders to go to the children of Israel as His messenger and liberator.
Then Moses said to God, "if I com to the people of Israel and say to them, 'The God of your fathers has sent me to you,' and they ask me, 'What is his name?' what shall I say to them?" God said to Moses, "I AM WHO I AM." And he said, "Say this to the people of Israel, 'I AM has sent me to you.'"
I AM: the statement of the all-eternal. Every Hebrew male in those days was obliged to memorize the entire Pentateuch, so the Jews understood by Jesus' statement exactly who he was claiming to be. He was claiming to be God, so they sought his death for blasphemy.
So, if Jesus couldn't have been a bad man, and He couldn't have been a mad man, and He had to be who He said He is, and He said He is God, we must conclude that God exists.