This is the story of a set of ideas that, in Britain and the United States, have dominated public opinion and public policy on the subject of poverty for nearly two centuries. From the beginnings of social science in Britain, these ideas have shaped the methods of poverty researchers. In their role as experts, these poverty researchers have in turn shaped the public debate on social welfare. They were among the founders of British social science, yet their writings on the poor have never been systematically examined to see how they obtained their information. This work does just that, tracing the influence of religious and economic ideas on their research about 'slum mothers'. Some of their names are well known: Charles Booth, Beatrice Webb, Malthus. Others, while less famous, were nonetheless influential in setting the agenda for poverty research down to the present day. But did they get it right?