The testing of intelligence has a long and controversial history. Claims that it is a pseudo-science or a weapon of ideological warfare have been commonplace and there is not even a consensus as to whether intelligence exists and, if it does, whether it can be measured. As a result the debate about it has centred on the nurture versus nature controversy and especially on alleged racial differences and the heritability of intelligence - all of which have major policy implications. This book aims to penetrate the mists of controversy, ideology and prejudice by providing a clear non-mathematical framework for the definition and measurement of intelligence derived from modern factor analysis. Building on this framework and drawing on everyday ideas the author address key controversies in a clear and accessible style and explores some of the claims made by well known writers in the field such as Stephen Jay Gould and Michael Howe.