Phillip E. Johnson on SETI
The Wedge of Truth (Downers Grove, IL: InterVarsity Press, 2000), p. 129.
[I]ntelligent design theorists need to explain why the vast majority of evolutionary scientists refuse to consider evidence of intelligent design in biology, scornfully dismissing the entire concept as "religion" rather than "science." [It] is because they identify science with naturalism, meaning that only "natural" (i.e., material or physical) forces may play a role in the history of life. Where the designer is itself some natural entity, such as a human being, evidence for design is welcome. Space aliens are also permissible entities, and so Carl Sagan's Search for Extra-Terrestrial Intelligence (SETI) radio telescopes scan the sky for signals, which they could identify as products of intelligence by precisely the same methods which intelligent design theory applies to biology. The difference is that scientific naturalists want to find evidence for extraterrestrial life, in part because they would count it as evidence that natural laws produce life wherever favorable conditions exist and hence as clinching the case for naturalism. They don't want to find evidence for what they think of as an "interfering" God, meaning a God who does not leave everything to law and chance. Hence they will refuse to see evidence of design that is staring them in the face until they are reassured that the designer is something whose existence they are willing to recognize.