New in paperback. Hardcover was published in 2013. Category mistakes are sentences such as 'Green ideas sleep furiously', 'Saturday is in bed', and 'The theory of relativity is eating breakfast'. Such sentences strike most speakers as highly infelicitous but it is a challenge to explain precisely why they are so. Ofra Magidor addresses this challenge, while providing a comprehensive discussion of the various treatments of category mistakes in both philosophy and linguistics.