In the 1990s, the majority of texts in cognitive psychology dealt with the details of cognitive processes as individually defined. Originally published in 1997, this book was different in providing an account of cognition that focuses upon the cumulative and shared nature of human enterprise. Each of us is seen as coming to understand our world by drawing jointly upon our individual cognitive resources and the collective resources of the larger community which have been (and are being) directed towards similar ends. Accounts of human cognition that underplay the significance of collective processes tend to compensate by investing the individual mind with whatever additional internal resources appear necessary to fill the gap. Accounts that treat human knowledge as a purely social construction err in the opposite direction by overestimating the frailty of human reasoning - especially once its products have been exposed to external criticism. The present book aims to adopt a more even-handed approach by letting both sides contribute to the debate. The result is a wide-ranging detour that starts off with cognitive science, then diverts into the domains of developmental and social psychology, before ending up in territory that is normally occupied by historians and evolutionary biologists. Although it was written with advanced undergraduate and postgraduate students in psychology in mind, it will also be of interest to students of other disciplines including cognitive science, education and philosophy.