Many “agnostics” suggest that elements of Intelligent Design are compatible with Evolution. Why isn’t it possible that there’s both a god who created life AND evolution via natural selection? This question represents a misunderstanding of evolution.
Evolution is dependent on *non-intelligent* selection.
That’s literally the whole point. All the predictions made by evolutionary theory rely on the consistency — the universality — of selection through completely natural processes. If there was some sort of “intelligent” interference with the process of descent with modification, there would be evidence. There would be inconsistencies in our observations that could not be explained with natural principles.
There are no such inconsistencies. This is a damning observation on two levels. First, Occam’s Razor demands that we not insert extraneous factors into a working formula. Colloquially, if it ain’t broke, it don’t need fixin’. More importantly, we must note that evolutionary theory doesn’t exist in a vacuum. The study of life is the tip of a giant pyramid of science. To understand how DNA works, we must understand how organic chemistry works. To understand that, we must understand basic chemistry. For that, we need atomic physics. For that, we need mathematics.
When we say that evolutionary theory works, we are implicitly relying on the entirety of the underlying sciences, each of which works precisely. If something was interfering with evolution, it would have to interfere with each of the underlying natural foundations of life. In other words, if intelligent interference with evolution was occurring, there would be evidence all over the scientific disciplines.
What if God caused life to exist, and then left it alone?
Many agnostics suggest that some intelligent entity is responsible for abiogenesis — the original “spark of life,” from which all current life evolved. This is much more possible than ongoing interference with evolution. However, this is not Intelligent Design. It doesn’t rely on “irreducible complexity.” It’s just a one-time directed movement of matter and energy which might not leave discernible evidence these billions of years later.
We might also suppose that aliens visited earth and planted the first life. It makes no difference. If evolution has been proceeding unmolested since the act of creation, then there is no need for mentioning intelligent design in evolution class. Or, put more directly: The study of abiogenesis is NOT the study of evolution, and has no bearing on evolutionary theory. Even if there was an intelligent origin to life, the mention of it is out of place in the discussion of evolution.
In short, the polite deference to the possibility of both intelligent design AND evolution is wrong. Intelligent origin is not the same as intelligent interference with natural evolutionary processes, and evolution is literally antithetical to intelligence. Evolutionary theory is the codification of non-intelligent selection.