Abstract: The first autism can only be understood in the context of the legal and institutional networks that enabled the spread of psychological theory as applied to infants and children in Britain in the early twentieth century. This chapter examines the integration of the concept of autism into psychological theory in Britain and the significance of the concept of autism in altering theories of social development in children. Theories of the 'social instinct' in infants and children developed alongside theories of intellectual development. The concept of 'mental deficiency' served as a convenient throwaway label for all infants and children who both psychologists and policy-makers thought were beyond help and not worthy of investigation. The chapter explores how the establishment of the unprecedented legal and political climate for children in Britain encouraged the first applications of the concept of autism.