The major reason unbelievers say they reject Gen 1 is because Gen 1 is said to be unscientific, or contrary to science. We know from modern cosmology, geology, botany, and zoology that that’s not how it happened.
But let’s hold that thought for a moment and compare that to another consideration. For many of the same unbelievers who reject Gen 1 on scientific grounds also subscribe to methodological naturalism. Here’s a representative statement of methodological naturalism:
There are two basic principles of science that creationism violates. First, science is an attempt to explain the natural world in terms of natural processes, not supernatural ones. This principle is sometimes referred to as methodological naturalism…Nonmaterial causes are disallowed.
When a creationist says, “God did it”, we can confidently say that he is not doing science. Scientists do not allow explanations that include supernatural or mystical powers for a very important reason. To explain something scientifically requires that we test explanations against the natural world. A common denominator for testing a scientific idea is to hold constant (“control”) at least some of the variables influencing what you are trying to explain. Testing can take many forms, and although the most familiar test is the direct experiment, there exist many research designs involving indirect experimentation, or natural or statistical control of variables.
Science’s concern for testing and control rules out supernatural causation. Supporters of the “God did it” argument hold that God is omnipotent. If there are omnipotent forces in the universe, by definition, it is impossible to hold their influences constant; one cannot “control” such powers. Lacking the possibility of control of supernatural forces, scientists forgo them in explanation. Only natural explanations are used. No one yet has invented a theometer, so we will just have to muddle along with material explanations.
For reasons I’ve given elsewhere, I think methodological naturalism is unscientific. But for the sake of argument, let’s play along with methodological naturalism.
If we take that methodology for granted, then what does it mean to say Gen 1 is unscientific? If would mean that things didn’t happen that way if you leave God out of the picture.
But this also means that if you do take God into account, then you’re in no position to say it didn’t happen that way. In fact, Eugenie Scott’s explicit justification for methodological naturalism is that If there are omnipotent forces in the universe, by definition, it is impossible to hold their influences constant; one cannot “control” such powers.
But in that event, she can’t rule out the possibility (or even probability) that Gen 1 is factual. Moreover, she can’t say Gen 1 has been falsified by the scientific evidence, for on her definition, scientific evidence can’t take divine agency into account. Therefore, it would be viciously circular for her to appeal to the scientific evidence against Gen 1 if, by definition, her method disallows supernatural causes. For in that case, she’s preemptively excluded potential counterevidence. By her own admission, allowing for the possibility of divine agency introduces uncontrollable variables into the process. But if science can’t make allowance for divine agency, then science can’t say what God would or would not have done in that situation. Indeed, on that definition, science can’t even say that divine agency is improbable in that situation. She’s disqualified science from making judgments about divine agency one way or the other. But that leaves the question open-ended.