This book is a collection of papers related to a workshop organized in Geneva in January 2017, part of a big event celebrating the centenary of Ferdinand de Saussure's famous "Cours de Linguistique Générale" (CLG). The topic of this workshop was THE FIRST PRINCIPLE stated in the second section of the first part of the CLG entitled: THE ABITRARINESS OF THE SIGN. Discussions are developed according to the three perspectives presented in the call for papers: (1) The details of the formulation of this principle in the CLG, its proper place (cf. the following sentence of section 2: "No one disputes the principle of the arbitrariness of the sign but it is often easier to discover a truth than to assign it its proper place"). Discussions about the question of arbitrariness of the sign in works by Saussure before the CLG are also welcome. (2) How the arbitrariness of the sign has been formulated and stressed before the CLG by other people than Saussure, in particular, but not exclusively, by people of the second part of the 19th century. Three important names: Boole, Peirce, Bréal. (3) The import and value of this principle and the criticisms it received after the publication of the CLG. Special focus will be given on the opposition between arbitrary sign and symbol (as characterized in the CLG: "the symbol is never arbitrary; it is not empty, for there is the rudiment of a natural bond between the signifier and the signified") in the context of mathematical and logical languages (visual reasoning), traffic signs and pictograms (cf. Neurath's Isotype), typefaces (cf. the work of Adrian Frutiger).