The Definition of Crime.--The best definition of crime and the simplest is that it is a violation of law. It is evident from this definition that crime is primarily a legal matter; and as laws vary from age to age and from country to country, so too the definition of crime varies. Nevertheless, because crime is a variable quantity that does not make it impossible of scientific treatment; for law itself is only one aspect or phase of the social life, namely, that which has to do with the control of conduct through organized social authority. Therefore, while crime is primarily a legal matter, it is also a social matter and has at the same time psychological and biological implications. While crime is an expression of social maladjustment defined by the law differently under different circumstances, it nevertheless has psychological and biological roots; and these we must take into account in a scientific study of crime. The simplest and best definition of the criminal accordingly is a violator of the law. However, because the criminal lacks social adjustment the causes of this lack of adjustment are very often in certain psychological and biological conditions of the individual. While the criminal is defined by the law differently from age to age, he is nevertheless under all circumstances the socially peculiar and sometimes the psychologically and biologically peculiar person. Under all circumstances he is a variation from his group; and whether the causes of his variation are psychological or biological is the problem that concerns us. But in the group of socially maladjusted persons whom we call criminals are many classes and it is necessary to note the chief of these classes before we can understand the many causes of crime.