It has long been shown that medieval builders primarily used geometrical constructions to design medieval architecture. The thought processes involved, however, have been considered to be remote from the natural philosophical speculations of the Scholastics, who, following Aristotle, had taken the basis of physics to be the study of dynamics, or change. However, investigations of the Expertises of Chartres, Florence, Milan, and other documents related to medieval building suggest that medieval architects, in speaking of their work, resort to recognizable dynamic arguments, structured similarly to the speculations of Scholastic philosophers. These dynamic explanations of structural behaviour persist at least into the 17th century, but thereafter lost out to the arguments based on statics made by modern scholars attempting to explain the endurance of these structures.