"He was his era's leading exponent of the Hirschian concept of Torah Im Derech Eretz. Exemplifying and expounding the teachings of Rabbi Hirsch, he gave the broadest possible definition to the term derech eretz. It embraced every facet of a Jew's human existence on earth: his means of livelihood, general decorum, civility, propriety of dress, interaction with his fellow, level of integrity in business and personal relationships, fulfillment of the law of the land, relationship to non-observant Jews, attitude toward purveyors of non-halachic "streams" of Judaism. The definition of derech eretz is as broad and varied as human experience, and wherever it applies, derech eretz must be subservient to Torah."
by Dr. Ernst J. Bodenheimer with Rabbi Nosson Scherman