Peasant and prince, crusader and scholar, humanist and mathematician, men of exemplary lives, born rulers and guides, such were the builders of Notre Dame of Paris, and their ability and sincerity live eternally in their work.[82] They gave free wing to the soul in raising their great church, while they cheerfully accepted the human law of working within limits. No cathedral in France shows more clearly the relation between builders and building, more clearly vindicates the ideals of its age. The partisan historian may cite his instances to prove that the religion of that age was superstitious. While Notre Dame stands, such charges are refuted. It is a historical document as potent for the vindication of the truth as the _Divina Commedia_ itself. When Bishop Guillaume d'Auvergne had finished the towers of Notre Dame he caused to be made the open arcade from which they emerge, as from a royal peristyle. About the same time side chapels were inserted between the buttresses, and the line of small rose windows, which had hitherto marked the triforium story, was done away with, in order that the clearstory windows might be lengthened. Only step by step were the builders learning that they might open the entire space between the active members of a Gothic structure; the upper windows of Chartres had passed on the lesson to Paris. The plan of the first architect was adhered to throughout, and since the later masters-of-works were likewise natives of the Ile-de-France and innate in them a classic restraint and a hardy daring (the hall-mark of the best Parisian art to this day), the cathedral of Paris was homogeneous. Midway in the XIII century Jean de Chelles, a precursor of Rayonnant Gothic, lengthened the transept arms by a bay and finished them with admirable façades. His name, and the date 1257, are cut on the foundation stone of the south façade. The sculpture of that southern entrance honors St. Stephen, since on the site had once stood a church dedicated to the first martyr; the tympanum of the door is another _chef-d'oeuvre_ of Notre Dame. Jean de Chelles was the first to use perforated gables. It is thought that on the north façade worked Pierre de Montereau, the architect of St. Denis. As the XIII century merged in the XIV Pierre de Chelles, probably a son of Jean, directed the making of the apse chapels and the superb flying buttresses which leap unhesitatingly over chapels and aisle and tribune gallery. He added the big tribune windows with gables.