As Claude Frollo had passed through nearly the entire circle of human learning—positive, exterior, and permissible—since his youth, he was obliged, unless he came to a halt, ubi defuit orbis, to proceed further and seek other aliments for the insatiable activity of his intelligence. The antique symbol of the serpent biting its tail is, above all, applicable to science. It would appear that Claude Frollo had experienced this. Many grave persons affirm that, after having exhausted the fas of human learning, he had dared to penetrate into the nefas. He had, they said, tasted in succession all the apples of the tree of knowledge, and, whether from hunger or disgust, had ended by tasting the forbidden fruit. He had taken his place by turns, as the reader has seen, in the conferences of the theologians in Sorbonne,—in the assemblies of the doctors of art, after the manner of Saint-Hilaire,—in the disputes of the decretalists, after the manner of Saint-Martin,—in the congregations of physicians at the holy water font of Notre-Dame, ad cupam Nostroe-Dominoe. All the dishes permitted and approved, which those four great kitchens called the four faculties could elaborate and serve to the understanding, he had devoured, and had been satiated with them before his hunger was appeased. Then he had penetrated further, lower, beneath all that finished, material, limited knowledge; he had, perhaps, risked his soul, and had seated himself in the cavern at that mysterious table of the alchemists, of the astrologers, of the hermetics, of which Averroès, Gillaume de Paris, and Nicolas Flamel hold the end in the Middle Ages; and which extends in the East, by the light of the seven-branched candlestick, to Solomon, Pythagoras, and Zoroaster.