Positive philosophy emerged at a time of profound social change. The American and French revolutions, the consolidation of a powerful middle class, and the dawn of the industrial revolution all marked these social changes. Among the founders of the positivist school of thought and, according to some, the first modern sociologist was Claude Henri de Rouvroy, Count of Saint-Simon. Positivists focus on cause and effect relationships. Causality is established when three to five conditions are met: (1) the presumed cause precedes the presumed effect in time, (2) the presumed cause and the presumed effect are empirically correlated with each other, and (3) the observed empirical correlation between the presumed cause and the presumed effect are not spurious, that is, the empirical relationship cannot be explained as being due to the influence of one or more others factors. A second difference is that positivists assume that criminals are fundamentally different from noncriminals, whether biologically, psychologically, sociologically, or some combination of the three. Positivists look for such differences through scientific research. When differences are noted, classifications or categories, such as criminal and noncriminal, are created. Third, positivists assume that social scientists, including criminologists, can be objective or neutral in their work. Fourth, positivists often assume that crime is caused by multiple factors, such as hormonal imbalances, subnormal intelligence, inadequate socialization or self-control, and economic inequality. Fifth, positivists believe that society is based primarily on consensus on moral values, but not on a social contract, as classical theorists believed. It has recently been claimed that "the scientific study of crime actually began with biological theories in the late 18th century." century”, and that “until the beginning of the 20th century, biological theories and criminology were practically synonymous”. Biological theories of the causes of crime are based on the belief that criminals are physiologically different from non-criminals. Early biological theories assumed that structure determined function. In other words, criminals behave differently because they are structurally different. The cause of the crime was biological inferiority. The biological inferiority of criminals was thought to produce certain physical or genetic characteristics that distinguished criminals from noncriminals. It is important to emphasize that physical or genetic characteristics themselves are not the cause of crime; they were only symptoms, or stigmata, of a more fundamental inferiority. Psychoanalytic theories of crime causation are associated with the work of Sigmund Freud (1856-1939) and his followers. Freud did not theorize much about criminal behavior per se, but a theory of crime causation can be inferred from his more general theory of human behavior and its disorders..