Almost everything we do is based on our knowledge of the world around us: how we dress in the morning, how we go about our work, how we interact with other people - all these things rest on our understanding of how we know life. Knowledge might be seen as the most central as well as the most under-researched trait of social life: we mainly think of knowledge as either technical (scientific knowledge) or formal (as bestowed by academic education). The things that we know are obscured in our everyday routines, not revealing their true status as 'known' - until critical moments demand it. This book establishes a fundamentally social understanding of knowledge.