From the preface:
"... the Copernican Principle, or the Principle of Mediocrity ... is far more than the simple observation that the cosmos doesn't literally revolve around Earth. ... This optimism found its practical expression in the Search for Extraterrestrial Intelligence, or SETI, a project that scans the skies for radio transmissions containing the "signatures" of extraterrestrial intelligence. ... Although attractive to those of us nurtured on Star Trek and other fascinating interstellar science fiction, such certainty [the existence of extraterrestrial intelligence] is misplaced. ... Recent discoveries from a variety of fields and from the new discipline of astrobiology have undermined this sanguine enthusiasm for extraterrestrials."