The Pilgrim's Progress is accepted in the canon of children's literature due to its early adoption by child readers and because of its outstanding qualities. This thesis explores some possible reasons for the work's popularity and longevity. A New Historicist approach suggests the relevance of Bunyan's pilgrim hero and his narrative to each of the three centuries since the work's first publication. It focuses particularly on the interaction between society, child and text, considering the societal and psychic dimensions. History and Developmental Theory, including that of Faith Development, are drawn on as particular resources. A propositional model provides visual explanation for the interactionary role of the components and suggests a scientific basis for the relevance factors. A broad sample of copies of The Pilgrim's Progress, published from 1678 until 1994, is surveyed in order to test the hypothesis that the hero is a changing one, affected by society's changing norms and ethos. Bunyan's influence on writers for children over the three centuries is also considered, leading to recognition of The Pilgrim's Progress as a prototype for children's literature.