Any collection runs the risk of becoming a collage that admits no firm focus. At the outset, therefore, we pursue the sharpness of image that all our contributors deserve as a setting for their own work. Consequently, the conceptual frames for the book are to be found in the first chapter, whose title, “The Abilities of Mankind,” deliberately echoes Charles Spearman. Although that choice of words may provoke comparison with Spearman's great work The Abilities of Man, we beg to limit comparison to one aspect only. Spearman's book was restricted by its data base: Ours is expanded by it. The challenges he set 60 years ago have filled the scholarly journals with data from every continent. The richness and diversity of human ability have been demonstrated in every culture, but the literature is scarcely better known to the great majority of students of human abilities than it was to Spearman himself.

The work of the authors of this volume owes much to empirical sources that are unknown, neglected, and ignored in “mainstream” psychology. A realistic theory of the abilities of man can be founded only on evidence from all of mankind, not from one subgroup. Moreover, the pursuit of scientific truth in any field that has lacked theoretical closure and has consequently suffered an overabundance of speculation is not straightforward: But the effort has to be made if the measurement of individual differences in cognitive skills and abilities is to remain a psychological enterprise worthy of sustained scientific attention.