This chapter lays the theoretical foundation of the book, defining prophecy as a non-technical, or inspired, form of divination, in which the prophet acts as an intermediary of divine knowledge. It is argued that prophecy is as much a scholarly construct as a historical phenomenon documented in Near Eastern, biblical, as well as Greek textual sources. The knowledge of the historical phenomenon depends essentially on the genre and purpose of the source material which, however, is very fragmentary and, due to its secondary nature, does not yield a full and balanced picture of ancient prophecy. The chapter also discusses the purpose of comparative studies, arguing that they are necessary, not primarily to reveal the influence of one source on the other, but to identify a common category of ancient Eastern Mediterranean prophecy.