This is a pretty popular trope that creationists and fundamentalists often level against atheists and scientists. I’ve termed it the faith gambit. It goes like this. Science deals with uncertainty; uncertainty requires faith; science therefore requires faith.
It’s a nifty little tactic designed to equate science with religion, aiming to elevate faith to the same position as science (or, conversely, to bring science down to the level of faith). Any atheist who’s ever discussed belief with a creationist has probably heard this argument or something akin to it before. Evolution is “only a theory” is a derivative of the idea that it takes faith to believe in science. The whole argument, though, is a fallacy. Faith is not the same thing as trust. One trusts science; one does not have faith in it. Let’s start with some simple definitions from Webster’s dictionary.
Gravity is a “theory” inasmuch as evolution is, yet it’s ludicrous to say that I “have faith” that a ball I throw in the air will return to the ground. Nobody would say that. Because there exists thousands and thousands of years of experience and experimentation and evidence that causes me to trust that the ball will return the ground.
Let’s take this a step further. A common thing I hear from creationists and other fundamentalists is something like the following: “When you drive over a bridge, you have faith that the materials will hold, don’t you? You have faith the the engineer did his job well, don’t you? You have faith that none of the workers cut corners on the job, don’t you?” None of these things require faith.
I can stand at a bridge every day for a week, a month, or a year, and watch car after car drive over with without any problems. I can inquire as to the competence of the engineer. I can look into his background and other projects. I can actually go and physically inspect the bridge to test the materials and construction. There is a whole body of evidence that would lead me to trust that the bridge is safe; no faith required.
How can this be extended to God? There is no body of experience or evidence or experimentation when it comes to God. I’ve never seen God, met God, witnessed a miracle. Nobody has discovered the Garden of Eden, and there is no geological evidence that there was a world wide flood within the last 6,000 years. A belief in God is a belief without proof; belief that a bridge will not collapse when I drive over it is belief based on evidence, things I can test and measure.
Of course, the creationist or fundamentalist will come back and try and tie this to a hypothesis which science cannot test, like the big bang theory. They will contend that since it’s impossible to go back in time and observe the big bang, and since it’s impossible to recreate the events for experimentation, that any belief in the big bang will require some degree of faith. Again, though, the difference is in the evidence.
The fact that the universe is expanding, for one thing. If God created everything, the entire universe, exactly as we see it today, I see no reason why we should see expansion. There is also the recent discovery of the gravity waves predicted by cosmic inflation and the big bang by BICEP2. If it walks like a duck, and quacks like a duck…it’s probably a duck. It’s Occum’s razor: if all of the evidence points to an explosion from a central point, then the simplest explanation is an explosion from a central point.
Again, creationists and fundamentalists will take a reductionist point of view and argue that it’s impossible to know what created the big bang and so forth. To which I would say that that isn’t indicative of the validity of the theory; it simply means there are more things to discover, to understand. It doesn’t automatically require a supernatural explanation.