Sometime before 1292 Isarn wrote a 700-verse poetic dialogue in Occitan between himself and a fictitious Cathar bishop named Sicart de Figueiras.
Novas del eretge ("News of the Heretic"), or The Controversy of Izarn, with an Albigense Theologian, as it is known, is a long diatribe against Catharism and its alleged doctrines.
Isarn is sometimes inaccurate, but his ignorance, and that of many Catholics, as to the particulars of Cathar dogma, is probably the result of the meetings in thickets and bushes which he describes.
He is convinced moreover that the Ja no fara crezens heretje ni baudes / Si agues bon pastor que lur contradisses ("Yet they would not believe heretics (Cathars) or Waldensians / If they had a good pastor to contradict them [the heretics]").
Isarn initially portrays the converted heretic as desirous to keep his conversion a secret so that he may easily teach his followers the true faith.