Why Intelligent Design cannot be scientific

We can look at the faces of U S Presidents carved on Mount Rushmore and know they were designed because we can come up with precise explanations for how human beings could have done it. We know human beings exist and that they are capable of doing such work. Likewise, we can examine a crime scene, knowing that human beings exist and are capable of committing crimes like robbery and murder, and how such crimes can be committed. But we know NOTHING directly about the supposed Designer of life on Earth or how he could have operated in the design process. Without that knowledge, Intelligent Design has no real scientific applications. It is nothing more than an appeal to religious prejudices.