This chapter examines Thomas Hobbes's key political ideas. After providing a short biography of Hobbes, the chapter traces the development of his political theory as articulated in the Leviathan. In particular, it considers whether Hobbism rests on the assumption of egoism and whether Hobbes's theory depends on the idea of a social contract. It also describes the sequential composition of the three versions of Hobbes's theory and shows that his basic assumption about human nature is a form of solipsism. According to Hobbes, our thinking is necessarily self-referential, which need not be equivalent to holding that we are necessarily self-interested (egoistic). The chapter concludes with a discussion of Hobbesian contractarianism, agency, and authorization as well as three strands of contractarian reasoning to illustrate the importance of the idea of consent in Hobbes's political arguments.