Abstract
Three areas on which the precise contours of the voluntary principle were open to question were: 1. government financial aid to the human services provided by religious organizations, such as education and social work, 2. government promotion of general religious ideas through non-financial, non-coercive means, such as prayers in public schools, and 3. constitutional protection of the private religious conduct of churches or individual believers against restrictions by general laws not aimed at religion. History is reviewed here to explore how the voluntary principle contained ambiguities with respect to each of these three areas. Translating that history into the present is also discussed.