This little volume brings together short statements and essays autobiographical in tone, in which Dr. Tillich described the points at which he had found himself ""on the boundary"" between two elements or positions. Quoting himself to the effect that ""The boundary is the best place for acquiring knowledge,"" he points out the ways in which these boundary situations have contributed to his thought. The general sequence is chronological, beginning with, ""Between two temperaments"" which describes the ""boundary"" between the characteristics of his parents, and proceeding through his years as a youth, a student, and a teacher and social thinker in Germany, to the new situation he found upon emigration to this country. The concluding retrospect seems to indicate that the material was written ""as I approach fifty."" The book gives added personal illumination to the general development of Dr. Tillich's thought, and will be read with interest by the large audience he commanded among all ranks of people.