This collection of essays serves both as an introduction to Ruth Millikan's Language, Thought, and Other Biological Categories and as an extension and application of Millikan's central and controversial themes, especially in the philosophy of psychology. Ruth Millikan's extended argument for a biological view of the study of cognition in Language, Thought, and Other Biological Categories caught the attention of the philosophical community. Universally regarded as an important, even brilliant, work, its complexity and dense presentation made it difficult to plumb. This collection of essays serves both as an introduction to that much discussed volume and as an extension and application of Millikan's central and controversial themes, especially in the philosophy of psychology