Science is not about the search for truth in the metaphysical sense because it is limited to testing only the physical realm [that is, it can only come up with naturalistic conclusions]. Some of you said that this presupposes materialism and is thus unfair because it "loads the dice" so to speak [by limiting the possible conclusions]. Perhaps so, but there is no way around this. "God did it," is not a hypothesis that can be adequately tested on the physical level.
Here's a story to illustrate why this approach is detrimental to science:
Imagine a geologist is in a jungle, collecting rock samples. He comes across a very strange rock with pictures carved into it. "By Jove!" he says. "I've discovered a new type of rock formation! Let's get to work determining which natural process produced this." His guide laughs and tells him that, clearly, some intelligent person purposely carved the pictures into the rock. The geologist scoffs at the suggestion, carefully explaining that if geologists answered difficult questions about appearances of design by simply saying "some guy did it" they would never discover the real truth.
When the guide tells the geologist that his position is actually preventing him from finding the real truth, and he should not limit the possible conclusions in this way, the geologist responds indignantly, "There's simply no way around this. I'm a geologist, and I only study physical rocks, not some possible being in the past who can never be tested."
Not only is this geologist extremely foolish and unscientific by allowing his philosophy to prevent him from following the physical evidence where it leads, but he will also waste the rest of his life fruitlessly trying to discover the natural, random process that created the "unusual rock formation."
Intelligent design merely postulates the existence of an intelligent designer based on physical evidence. No, we can't test God Himself, but neither can SETI scientists test far-off alien sources of intelligently designed messages. Those scientists, like ID scientists, will study the physical evidence they obtain, recognize the marks of intelligence (or lack of them), and come to conclusions about the sources. None of this is unscientific.