This article discusses the thesis that a subject can have a concept, think thoughts containing it, that she incompletely understands. The central question concerns how to construe the distinction between having a concept and understanding it. Two important versions of the thesis are distinguished: a metasemantic version and an epistemic version. According to the first, the subject may have concept C without being a fully competent user, in virtue of deference to other speakers or to the world. According to the second, the subject may have a concept without being able to provide a proper explication of it. It is argued that whereas the epistemic version is plausible, the metasemantic version faces some challenges. First, it needs to be explained precisely how deference enables a speaker to have C. Second, metasemantic incomplete understanding is in tension with the idea that concepts serve to capture the subject’s cognitive perspective.
The purpose and plan of the Handbook is described herein. Key concepts in the contemporary literature on reasons and normativity are introduced, and the forty-four chapters that make up the main body of the Handbook are each summarized. In the process, important connections between the chapters are highlighted. A distinctive feature of the Handbook is said to be the way in which it surveys work on normative reasons in both ethics and epistemology, focusing, when appropriate, on issues concerning unity or lack of it in different domains. It is noted that discussions of reasons and normativity in philosophy of language, philosophy of mind, and aesthetics are also surveyed in the Handbook.