"We understand the term Project to refer to any unit of purposeful experience, any instance of purposeful activity, where the dominating purpose, as an inner urge,

(1) fixes the aim of the action,
(2) guides its processes,
(3) furnishes its drive, its inner motivation."

Source: William Heard Kilpatrick, "The project method", Teachers College Record 19 1918, pages 319-335; see also R. L. Church, and M. W. Sedlak, Education in the United States: An interpretative history. New York: Free Press, 1976; L. A.Cremin, The transformation of the school: Progressivism in American education, 1876-1957. New York: Knopf, 1961.