Arnau showed a particular taste for the genre of aphorism, which was highly useful in teaching because of its mnemonic value.
- Aphorismi de gradibus (“Aphorisms on De Gradibus”),written between 1295 and 1300: Arnau writes about the gradations of medicines and the mutual interactions of their components, defending the mathematical method developed by the Arab al-Kindi as the authentic interpretation of Galen compared to Averroes. Even though al-Kindi’s treatise had already been translated by Gherardo da Cremona, it was not understood by Western physicians until Arnau introduced the topic with aphorisms. In this method of creating medicine compounds of a given degree based on simple ingredients, the proportion of cold to heat geometrically rises as the qualitative degree increases arithmetically. The Aphorismi de gradibus were still used in Montpellier for 50 years and may have influenced the formulation of the physical mathematical law by Thomas Bradwardine in Oxford.
- Medicationis parabolae (“Parables on healing”, 1300), devoted to Philip the Fair, King of France, is a compilation of 342 aphorisms with Hippocratic inspiration which provide professional ethical guidelines and therapeutic instructions for the physician in the act of healing. It includes a surgical part which would go on to be cited by the great surgeons Henri de Mondeville and Guiu de Chaulhac. Its practical nature and concise form made this Arnau’s most widely disseminated work after Regimen sanitatis ad regem Aragonum, in both the mediaeval manuscript tradition and in the modern press.
- Commentum super quasdam parabolas (“Commentary on some parables”): Commentary on the Medicationis parabole by the same author. This project was abandoned soon after it started, after having explained only 15 aphorisms in total.
- Aphorismi particulares (“Particular aphorisms”), which must have been left unfinished, is a heterogeneous compilation of 162 aphorisms based on clinical observations of illnesses that affect the head, chest, abdomen and genitals.
- Aphorismi de memoria (“Aphorisms on memory”) is a set of 25 hygienic guidelines to strengthen the faculty of memory.
- Aphorismi extravagantes (“Extravagant aphorisms”) is 24 guidelines, most of them aimed at healing the joints.