1. The World that Exists.
The first piece of evidence for the existence of God is the world that exists (see Isaiah 40:26). The world is here. We see that some things actually exist (trees, clouds, mountains, planets, stars, universes, etc). How did these things come to be and why do these things exist? Something or someone must have caused them to come into existence. Suppose that nothing exists. Nothingness wouldn’t require an explanation. The moment that something exists, there has to be a reason or a cause. Every effect has a cause.
How do we explain the world that exists? Either nothingness exploded by random chance and resulted in everything that we see OR it came into existence by a creator God (see Gen.1:1. 1 Chron.16:26).
For many centuries, thousands of people have wrestled with this cosmological argument for the existence of God. Many have concluded that it is a compelling argument.
2. The Design in the World.
The second piece of evidence for the existence of God is the design in the world. Not only does the universe exist, there is an order, a beauty, as well as a sense of harmony and purpose to everything.
Popular scientist Stephen Hawkings puts it this way: “If the density of the universe one second after the big bang had been greater by 1 part in a 1000 billion, the universe would have re-collapsed after 10 years. On the other hand, if the density of the universe at that time had been 1 part less, the universe would have been essentially empty after 10 years. How is it that the initial density of the universe was chosen so carefully?” What are the chances? He goes on to say, “The odds against a universe like ours emerging out of something like the Big Bang are enormous. I think there are clearly religious implications.”
Who or what is responsible for this? The incredible design in the world seems to point to the existence of a designer. A random chance explanation is highly unlikely. It doesn’t pass the standard test of reason. Whenever, wherever there is purpose, order, design and structure, reasonable people know that someone was responsible for it. Unless we can demonstrate that the world is capable of creating itself in all of its intricate design, then God must exist.
Charles Darwin himself, the king-pin in the theory of evolution, in a chapter titled “Difficulties with the Theory” (from his book “The Origin of the Species”), says, “To suppose that the human eye with so many parts all working together could have been formed by natural selection seems, I freely confess, absurd in the highest degree.” The improbability factor is incredible.
Only an intelligent designer could have produced a human eye or the navigation system of a homing pigeon or the spinning ability of a spider.
Based on what we know today, I truly believe that atheism (not believing in any kind of god) is a much bigger leap of faith than theism (believing that God exists).
Read the story of Antony Flew whose defection from atheism was a result of the above two arguments. This is detailed in his book There is a God: How the World's Most Notorious Atheist Changed His Mind.