Intelligent design begins with the assumption that the world we line in was designed and created by someone or something. Then “evidence” is amassed to prove the assumption. The problem with this approach, from a scientific perspective, is that the “evidence” is culled and tailored to lead to a “proof” of the assumption.
The logic runs something like this:
I believe the universe was created. What evidence can I find to support that belief? As a first assumption, anything that is exceedingly complex, like a watch or a computer program, was designed and created via intelligence and could not have just appeared by the random working of physical laws. The universe itself is exceedingly complex. Therefore, it must have been designed.
The fallacy lies in that first assumption. Turbulence is a very difficult phenomenon to understand but it does not follow that the seemingly incomprehensible complexity of the whirls and flows of fluids in motion were designed to be exactly the way they are.
Let’s use Occam’s razor. Named for William of Occkham, who proposed it in the fourteenth century, it has been paraphrased in a variety of ways, including KISS (Keep It Simple, Stupid). Isaac Newton’s interpretation was “We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances.” In the current case, the meaning is that whenever there are two or more possible explanations of a particular phenomenon, the one that is based on the fewest and simplest unproven assumptions is most likely to be accurate.
Intelligent design begins by assuming that the world we live in was created by something or somebody and was designed to be exactly the way it is, and then uses that assumption to prove that it is true.
If, instead, we do not start with an assumption of a world that has been designed, we arrive at a very different conclusion. Did someone or something design the universe? Maybe. I have no proof that it did not happen that way. I see no evidence that indicates it was designed, either. It is a pointless exercise to try to arrive at a definitive answer when there is no factual evidence on which to base a decision. Anyone can, of course, assume that there was some sort of intelligent creator of the universe. But there is no need for such an assumption and no evidence to indicate that it is more likely to be true than the assumption that things are what they are because that is how it happened. A universe might have come into existence with slightly different values for some fundamental parameters, such as electric charge, but we would not exist in that universe. That does not imply that somehow the specific values we determine for fundamental constants and interactions were pre-determined. It simply means that those values must be what they are if we are to be able to exist and therefore measure them.
It is possible to assume that when you let go of an object it hits the floor because the Earth really likes it and wants to be as close as possible to it. Maybe that is the case. For that assumption to represent reality, however, it is necessary to assume that the planet has some sort of consciousness of its own. Instead, we call the determinant of that process “gravity.” We don’t know what that is, but it is a simpler assumption than giving awareness and desire to an inanimate object.
Exactly how did our universe come into existence? I don’t know. You say “God did it.” That means you don’t know either.