The Roman Republic was a political system which, in theory, offered a stable balance between different social groups. In practice it was subject to conflict and change, which became particularly violent in the first century B.C. The introduction to this volume surveys the current research landscape and sets out the rationale for the volume's focus on institutional structures and ideological formations in seeking to understand the success and failure of the Roman Republic as a political system. It presents two underpinning arguments: that rules deriving from institutional norms could always potentially be overturned by the will of the people as manifested on a specific occasion, and hence innovation was a constant possibility; and that the complexity of the system as it evolved in practice was in tension with the binary simplicity of the Romans' narratives about the nature of their political constitution.