 Understanding is for Hobbes the work of the faculty of imagination, and crucially involves language. An account of the workings of language is thus crucial for his having an account of the workings of the mind. For Hobbes, the mind contains sense, imagination, and the workings of language, and no further rational faculty, such as the Cartesian immaterial mind that can grasp natures by clear and distinct perception. His story about sensation, the formation of ideas, and the workings of imagination is supposed to explain how some of our thought works. But only with the further story about language and understanding in place does he have a full alternative to Descartes’s story about our cognitive faculties. For Descartes, sense and imagination are, as in Hobbes’s story, closely connected to the workings of the brain, but higher cognitive functions are performed by the immaterial mind. Hobbes denies the existence of that immaterial mind, and needs other accounts of those functions. This – combined no doubt with some independent interest in the topic – leads to Hobbes devoting a fair amount of attention to issues in the philosophy of language.