Taleb opens by explaining the central image in the book: the Black Swan. In the Old World, prior to the sighting of a Black Swan, all swans were believed to be white. Taleb uses this image as a metaphor for the following kinds of events: they are outliers, they are highly impactful, and they are often explained after the fact by narratives that result from the human tendency to process things by means of stories. According to Taleb, these "Black Swans" help explain the most significant movements in human history. Additionally, Taleb articulates the central idea of the book, which revolves around "blindness with respect to randomness, particularly the large deviations" (xix). Much of this blindness stems from an overreliance on the knowledge we have already accumulated and on expert opinions, which often don't take Black Swans into account. Before moving onto the first chapter, Taleb provides a roadmap for how the book is organized.

Taleb sets up the prologue like the structure of a philosophical essay: He establishes a central premise, offers a few guiding principles or disclaimers, and lays out how the argument is structured. Taleb refers to the book as a personal essay, despite spending very little time on his own personal story.