In surveying the literature on assessment of cognitive abilities in adults and children, it is easy to assume that the proliferation of test batteries and terminology reflects a poverty of unifying models. However, the lack of recognition accorded good models of cognitive abilities may reflect inattention to theoretical development and injudicious use of empirical methods to validate models. In contrast, the studies of Weiss and colleagues in this volume reflect an evaluation of a widely cited model of cognitive abilities, the Cattell-Horn-Carroll (CHC) model for understanding the construct validity of the Wechsler Intelligence Scales for adults and children. Using the CHC model as the basis for evaluating a test battery provides an excellent example of statistical analysis as theoretical evaluation, an approach long advocated by methodologists. In this commentary several specific aspects of model evaluation and refinement are also discussed.