In a favorable review of the intelligent design book The Design of Life, quantum physicist Ulrich Mohrhoff concludes that "There's no doubt in my mind that specified complexity is the 'smoking gun' of some other-than-human intelligence at work [in the origin of species], as the authors maintain...[the intelligence], however, could be very different from how it is conceived by theists." There's a link to his review on the left sidebar.
The design inference is a conclusion reached by a logical and mathematical re-analysis of the scientific evidence (available evidence published by orthodox Darwinist biologists in scientific journals,) that intelligence had some part in the origin of living forms, by designing or influencing the design of at least some of their features. But that conclusion itself is incapable of identifying the intelligence or intelligences involved. And it cannot determine whether the intelligence involved was supernatural, or arose by some natural process.
Also, the inference that intelligence designed some features of life, in itself leads to no conclusion about whether species, including humans, are the product of some sort of long process of evolutionary descent, which was influenced by intelligence: or whether humans were specially created, and had no lower ancestors. The latter view is what is properly called creationism. The claim that intelligent involvement necessarily means creationism, or is "intelligent design creationism," is false, and is either ignorant, or else is fraudulent propaganda. I am not personally a creationist of any sort.
So the theory sometimes called intelligent design, as it has been developed by those scientists who proposed it, is a broad perspective which is compatible not only with creationism, but also with evolutionary descent. It is thus possible to hold many different personal views on these questions. Mohrhoff is one of those who believe in evolutionary descent (as I do also.) And while many who conclude that intelligence designed some features of life are Christians or other theists in their personal religious views, Mohrhoff adheres to no particular religion; although he isn't a materialist. (There are also a few who are agnostics or atheists. They assume that the intelligence arose by some natural process.) Intelligent involvement is also compatible with the view that natural processes played a considerable role in the origin of living forms. Some take that view, while others do not. Personally, I see no particular reason to believe in God: I don't think that I have any special reason to believe in anything omnipotent, omniscient, or omnibenevolent. Intelligence of some sort may have played a role in the origin of species. But if it did, I adhere to no doctrine about exactly what the intelligence was. Possibly, for instance, it was some conscious or intelligent factor present within each different living thing, since life first appeared.
Some Darwin-fans claim, by the way, that the non-Darwinist views of scientists such as Mohrhoff are irrelevant, if they have no degree in biology. Apparently they don't realize that Darwin's own formal studies were in medicine and theology, not biology: he had no biology degree. It takes interest, ability and effort to make a contribution in any scientific field, but it doesn't necessarily require a degree in that field.
Except for one technical section on "specified complexity," Mohrhoff's review is quite readable. It's a good introduction to the absurdities that abound in Darwinism, and to the evidence that intelligence was involved in life's rise.