"The Urantia Book" states in its Foreword that more than one thousand "human concepts representing the highest and most advanced planetary knowledge of spiritual values and universe meanings" were selected in preparing the papers. The authors say that they were required to "give preference to the highest existing human concepts pertaining to the subjects to be presented" and would "resort to pure revelation only when the concept of presentation has had no adequate previous expression by the human mind." One of the authors wrote in Part IV: "I well know that those concepts which have had origin in the human mind will prove more acceptable and helpful to all other human minds."