Relations Between Mechanics and Architecture Through the History of the Parallelogram Law of Forces from Antiquity to 1800

The role played by the parallelogram law of forces is central to the structural disciplines. This chapter reviews the history of the parallelogram law by emphasizing the important role of the more specific study of the parallelogram of forces, mostly carried out in studies related to stability and in particular to the stability of construction. The story is not linear because it springs from pure mathematics with the discovery of the generality of the parallelogram law for vectors to the practical knowledge of stability, passing through the knowledge of the cathedral builders.