This book grew out of an article entitled "I.Q.," published in the Atlantic Monthly magazine in September 1971. I owe the editors, particularly Robert Manning and C. Michael Curtis, a debt of gratitude for their interest in the idea of such an article and then, after I wrote a draft, for their criticism and counsel. Later, when the article had swelled about fivefold, I was fortunate to have Esther S. Yntema, senior editor at the Atlantic Monthly Press, as a faithful and deeply insightful critic. Susan Herrnstein has performed her usual but invaluable service as my most objective reader. I have also been fortunate that the preparation and editing of the manuscript rested in the capable hands of Arlene Andrew and Sara Hill