According to the received tradition, the language used to refer to natural kinds in scientific discourse remains stable even as theories about these kinds are refined. Hence, scientists discover, rather than stipulate, that sentences like 'Whales are mammals, not fish' are true. In this illuminating book, Joseph LaPorte argues that scientists do not discover that sentences about natural kinds, like 'Whales are mammals, not fish', are true rather than false. Instead, scientists find that these sentences were vague in the language of earlier speakers, and they refine the meanings of the...

This book will appeal to students and professional in the philosophy of science, the philosophy of biology and the philosophy of language.

Joseph LaPorte offers a new account of the connections between the reference of words for properties and kinds, and theoretical identity statements. Some terms for concrete objects, such as "Hesperus" and "Phosphorus," are rigid, and the rigidity of these terms is important because it helps to determine whether certain statements containing them, including identity statements like 'Hesperus = Phosphorus', are necessary or contingent. These observations command broad agreement. But there has been much less agreement about whether and how designators for properties are rigid: terms like...