relationship to violent acts than drug use—the correlation between frequent drug use and committing violent crimes at high rates may be in large part due to users' involvement in the systemic violence of the drug trade or participation in the symbolic violence of the urban drug culture (Goldstein, 1989; Chaiken and Chaiken, 1990a; Altschuler and Brounstein, 1989).

Similarly, the existence of causal relationships associated with other correlates of violent behavior has been questioned, including such strong correlates as alcohol (Collins, 1989), mental illness (Menzies and Webster, 1989), and child abuse (Widom, 1989a,b). The absence of proved causal relationships does not mean that these correlates are useless for classifying and predicting violent behavior. The sections that follow illustrate that noncausal correlates can provide bases for meaningful utilitarian classification and prediction. However, unlike Tay-Sachs disease, the current state of knowledge is not even close to having an adequate understanding of the causes of violence that would be needed to classify violent offenders and to predict violence with great accuracy.

The "art" of classifying violent offenders is reminiscent of the traditional story of the classification of the elephant by a team of blind people—each one measuring a different part and variously describing the ear, trunk, leg, tail, or torso. Not only have researchers and practitioners attempted to describe different dimensions of the same "elephant," they have also examined elephants in herds of different age mixes, sex mixes, and settings.

Populations studied for classification of violence have included nationally representative samples of adults (Gelles and Straus, 1988) and youth (Elliott et al., 1989), populations of children (Loeber and Stouthamer-Loeber, 1987), youth and adults in "high-risk" areas (Goldstein, 1989; Fagan et al., 1986; Fagan and Weis, 1990; Simcha-Fagan and Schwartz, 1986; Williams and Kornblum, 1985), clinical populations (Lewis and Balla, 1976), defendants (Chaiken and Chaiken, 1987, 1990b), institutionalized populations of convicted offenders (e.g., Megargee, 1977; Chaiken and Chaiken, 1982), and institutionalized populations of psychiatric patients (Toch and Adams, 1989; Steadman, 1987).

Researchers and practitioners carrying out these classifications have been drawn from such diverse fields as biology, mathematics,