Christians believe that our primary purpose in life, our main reason for existing, is that we might glorify and enjoy God. From the Westminster Larger Catechism:
Q. 1. What is the chief and highest end of man? A. Man's chief and highest end is to glorify God, and fully to enjoy him forever.
But how can we believe that God exists? What reason do we have for believing in God in the first place? Well, the very next question in the Westminster Larger Catechism addresses that. God does not call us to believe in Him without reason, after all -
Q. 2. How does it appear that there is a God? A. The very light of nature in man, and the works of God, declare plainly that there is a God; but his word and Spirit only do sufficiently and effectually reveal him unto men for their salvation.
So, we have two parts to this:
1. Everyone alive has "the very light of nature" inside them, testifying to the reality of God and also lives in the midst of "the works of God," which also declare God's existence. Thus, everyone has an internal and external witness.
2. However, people do not come to faith in God due to these two witnesses, which everyone has. Rather, it is only the word and the Spirit which reveal God in a way that actually causes people to know Him.
Let's look at these . . .
Universal Internal and External Witness
"How can you believe in God when you see so much evil in the world?"
When I hear this question, I think of two responses:
1. "It's interesting that you think there's evil in the world. Where did you get that idea?" 2. "How can I not believe in God when I see so much beauty in the world?"
God and Evil
The existence of evil does not nullify the existence of God, That God's creation is plagued by sin, sorrow, sickness and suffering does not therefore mean that He didn't create it. Nor does it mean that He is solely and fully responsible for the current state His creation is in.
But the fact that we see and recognize evil in the world for what it is, and the fact that we feel outraged and want to do something about it, does, in fact, testify loudly to the existence of a good God. If Carl Sagan was right and "The cosmos is all there is or ever was or ever will be," then what's the problem? Do you think fish ever complain about how wet water is?
In other words, a purely materialistic explanation of reality cannot account for moral outrage.
"That's not right!" we cry as ISIS rapes young girls and decapitates those who resist. "How can anyone do this?" we cry when we see the video footage of Islamic militants beheading and burning people alive. But if we're just a random collection of molecules, life is just "the survival of the fittest" and "might makes right," so what's the problem?
The truth is that God's creation is broken, marred by sin and cursed. We know it. We feel it deeply in the face of injustice, senseless violence, oppression, genocide, cancer, death and disease.
Atheists are famous for saying, "You don't need God to be a good person," but what do they mean by that? Do you need to explicitly believe in God in order to have an internal moral compass, a sense of right and wrong, of empathy and justice? Of course not! In fact, some kinds of religion can distort, corrupt and degrade our internal moral compass: See ISIS.
But you don't get a true moral compass, a real sense of justice (or beauty or truth or love, for that matter) without a good Creator. These things don't arise from molecules by chance. In a materialistic, purely Darwinistic world, there's nothing wrong with the strong killing the weak or the powerful oppressing the powerless and there's no reason to grieve the death of the weak and diseased .
So, if there's no God, get over your outrage over evil. There's no such thing! Some people do this, of course- or, they say they do. Beauty is subjective and "in the eye of the beholder," while truth is purely a personal construct. "Evil" is just a name we use for things we don't like, like rape, murder or Brussels sprouts. It's all just a matter of taste. Societies set their own standards of right and wrong, and who are we to judge?
The social standard in America for generations was that Africans were sub-standard semi-humans and that systematically enslaving them was right and good. So, who are we to judge?
ISIS believes male Christians should be beheaded and female Christians should be raped and forced to marry their rapists. If they resist, they, too, should be beheaded.
Hitler believed that all Jews were a stain upon the face of the earth and should be exterminated. Who are we to judge another society's moral standards?
But we do. Because we know better. Because there is a God!
God and Beauty
Why should there be 20,000 species of butterflies in the world and why should we find them beautiful?
Why should there be so many countless shades and variations of green in trees and plants if it's all just chlorophyll for making food?
Why should dying leaves erupt in such an explosion of colors and beauty before falling to the earth?
Why should a sky full of stars or a rainbow after a storm take our breath away and fill us with joy and wonder?
The world is alive with color, beauty, splendor and majesty. This is not an accident and it testifies to the creativity of the Creator and to the beauty alive behind the madness and sadness of our world.
I am amazed by insects that look just like sticks and leaves. We can dismiss these amazing little bugs as "evolutionary adaptations for survival" or we can say, "Wow! That's amazing!" and allow the wonder to point us to obvious, to the Creator who made them, whatever the process might be that He used.
Word and Spirit
But the internal witness of our sense of justice and the external witness of the created world do not, by themselves, cause people to believe in God. This very fact itself confirms what the Bible says about humanity. In other words, the existence of atheists in a world so obviously created testifies to the truth of the Bible's verdict of humanity:
"For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who by their unrighteousness suppress the truth. For what can be known about God is plain to them, because God has shown it to them. For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse. For although they knew God, they did not honor him as God or give thanks to him, but they became futile in their thinking, and their foolish hearts were darkened. Claiming to be wise, they became fools . . ." - Romans 1:18-22 People suppress the truth about God by unrighteousness. They push down what is obvious and evident because, although they know God, they do now wish to honor Him or give thanks to Him. This is our natural tendency as fallen and corrupt human beings. Our thinking becomes futile and our hearts become dark,
So, how is is that some people do believe in God? Because God reveals Himself in His word and affirms His word by the internal testimony of the Spirit. Once again, we have an internal and an external witness, only this time the combined effect of the internal and external witness is effective. And once their testimony does effectively change our minds about God, then we are renewed in our minds and able to see the witness of creation and the internal light of nature for what they are, too.
In other words, once the Spirit works faith in us by the word, we don't just get two witnesses to God but four, We get the word and the Spirit, but we also get what God gives everyone, only now we're able to see it. In fact, we now see it so obviously that we wonder how everyone else in the world can miss it. But we need to remember that we missed it, too, until God opened our eyes through His word and His Spirit.
Does God give us good reason to believe in Him? Yes! Is the evidence for God;s existence clear, unmistakable and obvious? Yes! But we will not accept the reasons and we cannot see the evidence until God, by His word and Spirit, opens our eyes to see. Whose fault is that? It's only ours. Our eyes are stuck shut because we stuck them shut in rebellion.
Imagine a man whose eyes are shut tight as he is walking through a flower garden. Now imagine that his eyes have been shut tight his whole life, having never been opened ever. How could you convince him that he was walking in the midst of beauty and that the aromas he's smelling come from beautiful flowers. He cannot see them! But he cannot see because he will not see. Someone must first open his eyes!