An earlier comment suggested the possibility that if a god “turned up,”- i.e., appeared in some form that we humans could recognize, then it would be possible to determine using the scientific method to prove that he existed. But it wouldn’t. Because there are no forms under which a god could appear that we could be scientifically certain was divine. Think about it: how would God have to appear to convince scientists that it was a god and not a natural form?
In fact, millions of people believe that God has indeed already become manifest in several different ways. The most obvious manifestation is creation itself. Believers argue that everything has a cause, and if you keep going back, you ultimately have to reach a First Cause. This First Cause, for many people, is God. Many also believe that this God didn’t just create the universe, but continues to be involved in it, punishing and rewarding those who obey or disobey his commands. Others think that, having set the process of creation in motion, God now lets it proceed without further divine interference.
The claim that there must be a first cause sounds like a rational argument. Why isn’t it considered scientific? At the risk of doing violence to philosophical thought, one simple reason is that it is not based on empirical evidence. Faced with our universe, the scientist does indeed ask “how did it get here?” and has provided one possible answer in the form of the Big Bang. Some religious thinkers have argued that learning about the Big Bang is like seeing “the face of God.”
But the scientist doesn’t say it is God that has been found. He and she instead asks questions like “What caused the Big Bang?”,, “have Big Bangs happened before? will they happen again?” “what is the history before the Big Bang?”. Scientists themselves may personally believe in a Creator God, but they do not use the scientific method to find him. They use the scientific method to find causes which reflect the natural laws of the universe. They are not looking for a divine First Cause outside the natural world.
Another significant manifestation of God for many is Jesus who they believe was indeed truly God in human form. Throughout the last two millennia, millions of people have lived and died in the firm belief that this is so. The problem, from the scientific point of view, is that there is no empirical way to determine whether or not Jesus was God’s son in a way that other humans are not. Again, there are many scientists who are committed Christians. But there are no scientists who can say that they believe in Christ because they have proved this to themselves through an application of the scientific method.
Fundamentally, the problem is that the scientific method doesn’t actually look for proof that something is true, but that it isn’t true. It’s the principle of falsifiability that is based on what is called “the rejection of the null hypothesis.” What this means in less fancy language is that science looks for evidence that proves that something can’t be true. The conclusion that something must be true is based on the evidence that the opposite possibility has been proved to be wrong.
For example, a drug company wants to know if a particular medicine it wants to market will have undesirable side effects. To test whether headache might be a side effect, the null hypothesis is “this medicine will not result in headaches.” It gives the medicine to a selection of volunteers, and if it is followed by headaches, the company rejects the null hypothesis, and agrees to publish a warning that a side effect of the medicine may be headache. If nobody gets headaches, the company can only say “we have found no evidence that it causes headaches.” As we know, once a medicine is on the market, it is quite possible for evidence to emerge which does indeed result in the rejection of the null hypothesis which was that the drug has no known side effects
The problem with testing the hypothesis “There is no God” is that there are no conditions which we might observe which would prove that either that there must be a God, or alternatively there cannot be a God. Some people say that evil and suffering in the world is why they say there isn’t a God. But other people look at the same evil and suffering and say that it is God’s punishment for our sinfulness, or that a greater good will come from the suffering, even if we don’t understand how.
In other words, there is nothing that might happen that would prove scientifically that God does or does not exist.
And that is why the question of God is not a question that can be ever be answered by applying the scientific method.
It is a question of faith, not one for science.