What Engineers Know and How they Know It: Analytical Studies from Aeronautical History (The Johns Hopkins University Press, 1990) (ISBN 0-8018-4588-2) is a historical reflection on engineering practice in US aeronautics from 1908 to 1953 written by an accomplished practitioner and instructor. This period represents the dawn of aviation which was fraught with uncertainties and numerous paths to many possible worlds. The book captures two main conclusions from this period.