This book provides a synoptic and accessible history of the development of political ideas within the Labour Party. It traces the complex relationship between power and political thought and illustrates how Labour's political ideas have been shaped and formed by the Labour Party's political experience. It presents 'labourism' or trade union politics as a clear theory and stresses its importance in understanding the different phases in the party's history, arguing that it constitutes the bedrock of the party's thought and that its crisis has caused the recent changes in party ideology.