or purely written languages with no spoken form or a spoken form that would vary greatly according to the native language of the reader.

Leibniz and the encyclopedists realized that it is impossible to organize human knowledge unequivocally in a tree diagram, and consequently to construct an a priori language based on such a classification of concepts. Under the entry Charactère, D'Alembert critically reviewed the projects of philosophical languages of the preceding century. After the Encyclopédie,