Our daily lives are full of vagueness or fuzziness. When we describe someone as “tall,” for example, it is as though there is a particular height beyond which a person can be considered “tall.”

In Not Exactly: In Praise of Vagueness, Kees Van Deemter cuts across various disciplines — including artificial intelligence, logic, and computer science — to illuminate the nature and importance of vagueness. Van Deemter shows why vagueness is both unavoidable and useful, and he demonstrates how tempting — and how wrong — it often is to think in terms of black and white, instead of the richly graded spectrum of the world around us.

Vagueness, the author argues, allows us to focus on what matters, leaving out irrelevant details, and adding texture to what would otherwise be unintelligible facts. The embrace of vagueness, however, comes at a price, for when degrees of grey are accepted, concepts like truth, belief, and proof lose their power, and we are banished from that paradise in which truth and falsity are the only possibilities.