The last of the three series of lectures on general linguistics which Saussure gave in Geneva during the academic year 1910–1911 provided the editors large portions of the text of the Cours de linguistique générale. However, the editors completely modified the order of these parts in relation to the plan that Saussure had mapped out and followed inhis lectures. These changes obscured the relationships between the parts and certain fundamental ideas of his thinking. In particular, they eclipsed the role which played, for Saussure, ‘the laws which universally are at play in language’ and search he conducted along those lines. These laws also imposed important limits on the arbitrariness of the sign. In the third course, Saussure shows more than one of those limits: the necessarily systematic nature of language; the effects of phonetic change; the delimiting temporality of any language. The spacial diversity of languages finds its origin in the temporal diversification under the influence de ‘la masse parlante’. It is due to this variability of any system that, according to Saussure, we find opposition between universal laws, on the one hand, and the written languages which cover up the constant variations encountered in spoken language. As a careful philologist, Saussure could not fail to pay attention to the written languages. Still, they become, in as much as they interfere with spoken language, an element of variation.