"Freedom" has never been a fixed category or predetermined concept. Subject to multiple interpretations, its definition has been created and recreated by historical contingencies and social conflicts. Eric Foner traces how the existence of slavery helped to shape the understanding of freedom by Americans both white and black from the colonial era to the end of Reconstruction. He pays particular attention to the metaphorical uses of "slavery" by groups seeking to expand prevailing definitions of freedom (such as the labour movement's critique of "wage slavery", and criticism of the "slavery of sex" by early feminists) as well as to the debate over the meaning of freedom unleashed by the destruction of slavery during the Civil War.