Most books on writing assume that the sole purpose of writing is communication. These manuals seldom go beyond teaching how to avoid the problems of punctuation, grammar, and style that at one time or another ensnare the best of writers. Few, if any, of these books explore writing as a way of shaping thought.

V.A. Howard and J.H. Barton, two Harvard researchers in education, take a radically different approach. While they agree with their predecessors that an important function of writing is the clear, direct expression of thought, they point out that many of our thoughts first come...