THE history of philosophy and the history of civilization are distinct yet inseparable. Ideas do not arise in vacuo: they are often suggested by life itself; and contrariwise, ideas do not become buried in dusty treatises: in many instances, they influence various sciences and arts, or find their way into man's material environment.
In studying philosophy, we must beware, therefore, of regarding thinkers and their contributions to culture in isolation from events of the preceding and the succeeding ages. The student should not learn philosophy torn out as it were of the actual context of life.
We find it desirable, for these reasons, to begin our brief survey of the life and work of individual thinkers with a bird's-eye view of the three centuries of American thought up to the present day, in the form of a chart demonstrating complex but organic relations between philosonhv and history in general. The chart gives each thinker's date of birth and date of death, connected by a black vertical line. This line is placed toward the right or the left, to indicate the type of his philosophy on the scale of idealistic or naturalistic leanings. His name is printed higher or lower on his life line, depending on the approximate period of his most fruitful work.
Side by side with these data one can find references to facts of great cultural significance-printed in red-such as major wars, political events, founding of great universities, basic inventions, and the names of the most influential foreign scientists and philosophers.
It was most difficult, of course, to decide upon our list of American thinkers, twenty-five in all, to be included in the chart and the following text.
It seemed advisable, first of all, to abandon a purely professional standpoint and to select at least a few outstanding thinkers, not ordinarily called philosophers; among them are found William Penn, Abraham Lincoln, Walt Whitman, and Robert G. Ingersoll. On the other hand, men like Alexander B. Johnson ( 1786-1867),