Autism is an essential concept used in the description of child development and its variances. This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book traces the radical transformation of the concept of autism in Britain, exploring the reasons behind the shift and the impact that it has had on psychological sciences relating to infants and children. It locates changes in psychological theory in Britain in relation to larger shifts in the political and social organisation of schools, hospitals, families and childcare. The book explores how government entities have dealt with the psychological category of autism. The history of child psychology in Britain has largely been compartmentalised into the history of child guidance, the history of intelligence testing, the history of special education and the history of psychoanalytic theory.