Humanity early on made sense of the movements of the planets, stars, sun and moon, that part of nature furthest removed from us. It has taken the whole span of civilisation for our focus of interest to be turned in upon our own nature, at least from a scientific rather than a religious, philosophical, or artistic point of view. The lens that makes possible this scientific examination of personality is our affinity with other apes and simians. These relatives are social animals and like us spend the greater part of their lives in social pursuits. This book sets out, therefore, to distinguish what we share with these zoological relatives and what distinguishes us from them at least in degree; what drags us back and what potentially sets us free by setting free our intelligence.