Abstract
<jats:title>Abstract</jats:title> <jats:p>This chapter presents a brief history of the International Classification of Diseases and Related Health Problems (ICD) and the Diagnostic and Statistical Manual of Mental Disorders (DSM) classifications of mental disorders, specifically highlighting and contrasting the categorical and dimensional components of those systems. Using four theoretical dichotomies of (a) rational versus empirical development, (b) descriptive versus etiological concepts, (c) biological versus psychological descriptions, and (d) “lumpers” versus “splitters,” the chapter characterizes developments in these two major classification systems over time. For example, early diagnostic systems were highly focused on the presumed etiology of the disorders as an organizational principle, but these etiologies have been questioned, and more modern systems became more neutrally descriptive. The evolution of these systems can be seen as reactions to previous viewpoints and problems, culminating in movement toward dimensional diagnostic systems, which will almost certainly generate a new set of problems for future generations to react against.</jats:p>