You can explain the workings of an internal combustion engine without resorting to any supernatural speculation. You also know that GM, Ford, Honda, etc., built that engine by the fact that is inside a Chevrolet, Ford, Honda, etc. vehicle and has a VIN imprinted on the engine block that identifies the manufacturer. If the natural universe can be likewise explained entirely without supernatural speculation, and if there is no indication of any creator, as there would be with an internal combustion engine, would it not be more reasonable to assume that the universe has no creator? The theistic scientist would then be holding to a contradictory position: accepting the picture of a universe that provides no evidence of a supreme being yet believing in such a being.
That conclusion doesn't necessarily follow from your premise.
Apparently, you believe then that faith is unnecessary for a belief in God. After all, if you could show that God existed via looking at physical evidence, then there's no need for faith. But conversely, if you can't show that God exists by looking at physical evidence, then God has no place in the methodological practice of science. The reason that I personally do believe in God has more to do with faith than with the evidence. Doesn't faith still mean believing without any evidence for that belief. That is not science, but that is where a belief in God comes from. It is not contradictory for someone to believe in God, yet to assume that this belief is not necessary to study physical evidence. You simply are considering what can be learned from considering the evidence without any reference to God. Think of it as kind of a game, ie. let's ignore any belief in God, and see what we can learn ONLY by looking at physical evidence. In a way it's similar to modern mathematics. At one time, for example, in geometry, mathematicians only studied geometry that seemed to have some correspondence with reality, ie. Euclidean geometry. For example, if you draw a line and a point, you can only draw one line parallel to the given line. However, it makes perfect sense to study a geometry where you could draw no lines parallel to a given line. You would just have trouble drawing or visualizing it, but it causes no logical contradiction. You could similarly have a geometry where you could draw an infinite number of straight lines through the point parallel to the given line. The point is that geometry became sort of a self contained exercise; anything outside of the geometry itself was irrelevant. Similarly, supernatural phenomena such as God lie outside of the scope of science and as such are irrelevant to science. BTW, I don't believe that you can look at physical evidence and explain the universe without reference to a Creator. Evolution doesn't attempt to do so. Even big bang theory really doesn't do this; it just pushes the question back a bit. What exactly caused the creation of the universe? Why did the big bang happen the way it did? Why are the laws of nature and the values of the fundamental constants what they are? These questions, I believe have yet to be fully explained by science, and may never be.
Yes, but you cannot fully explain how an engine was invented without discussing market forces. In other words, selection. No product as complex as an automobile is designed from first principles. Things get the way they are because unpredictable (not random, but nevertheless unpredictable) selective events occur.
It makes no difference to biological or product evolution how change occurs. Selection determines the ultimate direction of change, and selection is unpredictable.
The fundamental error of ID is in its assumption that complex systems can be designed from first principles, without an iterative process of production and selection.