That's a really good question—and it's an important question, because it's about life and death issues. And if God doesn't exist, then Christianity totally falls down.
Some things that I've thought about that prove the existence of God: firstly, creation.
When I look at creation, when you look around at the beauty of nature, you think it's so beautiful it's like a painting, a masterpiece—and so it makes me feel that there must be a master behind it, a master artist, a master designer.
And so that's one of the reasons that makes me think God exists—but I appreciate that not everyone looks at nature and sees a Creator behind it.
Another evidence for God is that we all have a conscience. We all know right from wrong: where do we get that from? That's God.
And a bigger proof is the man Jesus Christ. He lived and he died and he rose again—and he claimed to be God. And if that's true—if he is who he claimed to be—then obviously that proves God exists.
One of the things Jesus did was he was in a boat with his disciples, and this horrific storm came up. They were seasoned seamen and they were terrified—but Jesus just calmed the storm with a word, and immediately the waves and the wind obeyed him, and it was calm.
And I think only God could do that—and that shows that Jesus was God.
It's really worth thinking more about who Jesus is—go to a good local church, or talk to a Christian friend, to find out who Jesus is.
Another thing is the way God works in my daily life. He's not just the true God, but he's also a brilliant God. He's been with me since I became a Christian, walking with me—he talks to me through the Bible, and I talk to him in prayer. And he's just proved himself to be really faithful and trustworthy.
So four things worth thinking about—creation, conscience, Christ, and just the impact that God has on people's lives.