Scientifically-inclined people like me dismiss the idea of "intelligent design" when it is applied to the universe as a whole, or Earth in particular. It just is extremely unlikely that our world was designed by an intelligent being, rather than coming to be as it is through evolution's process of natural selection.
Strangely, though, even most scientists assume that history is the record of how we humans have designed cultures, civilizations, and such. So intelligent design isn't accepted as an explanation for how the natural world came to be, but it is accepted as an explanation for how the "built" world came to be.
Is this correct?
Why shouldn't whatever humans do fall under the same laws of nature as what other animals do? Sure, we're more intelligent (in some ways) than non-human animals, but are we capable of design, while those other creatures aren't?
In "The Atheist's Guide to Reality," Alex Rosenberg says no to the last question. It's an interesting argument, one which strikes at the heart of cherished societal and individual presumptions about how people think, decide, and act.
Darwin made good physics' claim to banish purpose from nature. The process he discovered underlies the appearance of purpose wherever it emerges, even in the human mind.
Not only are the individual acts of human beings unguided by purpose; so are their thoughts. Combine the purposeless but well-adapted thoughts of a lot of people over a long time, and the result is history. Could history have purpose, meaning, or a direction even when people lack them?
Sure, it could, if there were any purposes. But physics has already ruled them out. Science excludes God's designs, or some purpose operating in the universe to navigate events into some safe harbor hidden in the future.
There is no alternative to blind variation and environmental filtration in human history, so there is no source for meaning or purpose in our history.
What we're left with is nihilism.
Fortunately, Rosenberg says it is nice nihilism. "Nice," because humans (like other animals) naturally are driven to choose life over death, getting out of bed in the morning rather than laying around in a depressed, listless state.
Nice nihilism undermines all values. This also goes for the silly idea of the existentialist philosophers, who realized that science rules out meanings or purpose and so insisted that we each had to create them for ourselves.
...Existentialism didn't see the fatuousness of trying to create something that nature had ruled out as impossible. Creating purpose in a world that can't have any is like trying to build a perpetual motion machine after you have discovered that nature has ruled them out.
...Luckily for us, Mother Nature has seen to it that most of us, incuding the secular humanists, will get up most mornings and go on living even without anything to make our lives meaningful. The proof is obvious. There is nothing that makes our lives meaningful, and yet here we are, out of our pajamas.
The notion that we need something to make life meaningful in order to keep living is another one of those illusions fostered by introspection.