How can nothing cause something? The absence of something might seem to indicate a null or a void, an emptiness as ineffectual as a shadow. In fact, 'nothing' is one of the most powerful and effective ideas the human mind has ever conceived. This short and entertaining book is a lively tour of the history and philosophy of nothing, explaining how various thinkers throughout history have conceived and grappled with the mysterious power of absence -- and how these ideas about shadows, gaps, and holes have in turned played a positive role in the development of some of humankind's most important ideas. Filled with anecdotes, puzzles, curiosities, and philosophical speculation, the book is ordered chronologically, starting with the ancients and moving forward to the middle ages and the early modern period, then up to the existentialists and present day philosophy. The result is a diverting tour through the history of human thought, seen from a novel and unusual perspective.