The study of crime. Criminology is an interdisciplinary field that combines aspects of legal theory and the substantive legal disciplines with approaches based on psychology, sociology, and moral philosophy. Its subjects include the nature and definition of crime, its forms and incidence, its causes, and crime prevention. Historically, two main approaches have dominated, the classical school and the positivist school. The classical school of criminology emphasizes the role of free will and rational choice in criminal behaviour and the use of punishment to deter it. By contrast, the positivist school of criminology seeks the causes of crime in biological, psychological, and sociological factors largely outside the control of the individual offender. Most modern approaches to criminology can be seen to have their roots in one or other of these schools, although recent decades have seen the development of so-called “integrative” and “realist” theories that seek to combine elements of both. See also penology.