'If intelligent life is common in the Universe, where is everybody? In this comprehensive review, Duncan Forgan presents a range of possible solutions to this question, and in doing so covers a lot of ground on the topic of SETI (the Search for Extraterrestrial Intelligence). From the outset, Forgan recognizes that this topic demands a multi-disciplinary approach that encompasses 'all of human knowledge', and in particular, expertise not only in the 'hard sciences' but also in social sciences and the humanities.' Michael A. Garrett, The Observatory