Definitions persuade and identify as salient particular features of the environment. For example, the concept of a criminal career makes salient the age at which criminal behavior, begins the frequency of criminal behavior, and variations in types of criminal activities. Because these features are tied to important events such as prison crowding, crime prediction, and crime prevention, the concept of criminal career is significant. The link between crime definition and chronicity can lead to a continuum fallacy. The continuum fallacy is the fallacy of reasoning that because career criminals commit more crimes than other types of criminals, any group of criminals who commits more crimes than others others are career criminals. The continuum fallacy can also be found in studies of psychopaths who are sometimes fallaciously identified as being more aggressive, antisocial persons. A similar problem occurs in studies of the relation between crime and alcoholism. Studies that mislabel heavy drinkers as alcoholics may lead to mistaken conclusions about the effects of alcohol. With regard to research strategies, longitudinal studies are necessary to learn the temporal ordering among educational problems; antisocial friendships; and delinquency or among child aggressivity, parental rejection, and inconsistent discipline. Although longitudinal studies are not appropriate for answering questions related to crime distribution, they are probably the only means by which intervention can be fairly evaluated. Psychological hedonism does not always explain criminal motivation, and criminologists erroneously seem to believe that crime theory must account for the existence of crime. The author contends that criminologists should focus on theories that are less global than on theories that purport to explain crime completely. 14 references