Why SETI isn't like "intelligent design"

Writing on the space.com website (December 1, 2005), Seth Shostak of the SETI Institute debunks a common claim of the "intelligent design" movement: that "intelligent design" uses the same methodology, and thus is as scientifically credible, as the search for extraterrestrial intelligence. Summarizing, Shostak writes:

the champions of Intelligent Design make two mistakes when they claim that the SETI enterprise is logically similar to their own: First, they assume that we are looking for messages, and judging our discovery on the basis of message content, whether understood or not. In fact, we're on the lookout for very simple signals. That's mostly a technical misunderstanding. But their second assumption, derived from the first, that complexity would imply intelligence, is also wrong. We seek artificiality, which is an organized and optimized signal coming from an astronomical environment from which neither it nor anything like it is either expected or observed: Very modest complexity, found out of context. This is clearly nothing like looking at DNA's chemical makeup and deducing the work of a supernatural biochemist.