This book provides an account of the emergence of norms. Put very crudely, the main thesis of this book is that certain types of norms are possible solutions to problems posed by certain types of social interaction situations. The problems are such that they inhere in the structure (in the game-theoretical sense of structure) of the situations concerned. Three types of paradigmatic situations are dealt with. They are referred to as Prisoners' Dilemma-type situations; co-ordination situations; and inequality (or partiality) situations. Each of them, it is claimed, poses a basic difficulty, to some or all of the individuals involved in them. Three types of norms, respectively, are offered as solutions to these situational problems. It is shown how, and in what sense, the adoption of these norms of social behaviour can indeed resolve the specified problems.