The chapter looks at common assumptions about human nature and concepts that define classical criminology. Also, the chapter acknowledges the work of seminal classical theorists and discusses the deterrence theory. The chapter gives examples of rational choice theory and research testing deterrence. Over the years, classical theory has been used to explain crime. This theory continues to influence law and social control in society. The theory originates from the golden age of Greece (Miller et al., 2015). The proponents of the classical school of criminology focused on reforming the criminal justice system. However, neoclassical perspectives emphasize punishment and deterrence and are associated with conservative public policy. All classical and neoclassical theories are based on assumptions of human nature and behavior. Throughout the beginning of the nineteenth century, enlightened thinking regarding crime was based on the classical perspective. This theory and its basic assumptions about human nature and behavior are still thriving in the modern world.