Arnold studied medicine at Paris for twenty years, after which for ten more he perambulated Italy, visiting the different universities. He subsequently penetrated into Spain, but hearing that Peter d’Apono, his friend, was in the hands of the Inquisition, he prudently withdrew, and abode under the patronage of Frederick, King of Naples and Sicily, writing his tracts on medicine and his “Comment on the School of Salerno.” He is said to have perished in a storm during the year 1314, but a circular letter written by Pope Clement V. in 1311 conjures those living under his authority to discover, if possible, and send to him, the “Treatise on Medicine,” written by Arnold, his physician, who promised it to the Holy Father, but died before he could present it. In this case the date of his decease may be more accurately fixed at 1310. Arnold was, according to the custom of the period, charged with magical practices. François Pegna declares that all his erudition in alchemy was derived from the demon. Mariana accuses him of attempting to create a man by means of certain drugs deposited in a pumpkin. But he is justified by Delrio from these imputations, and the orthodox _Dictionnaire des Sciences Occultes_ considers that Clement V. would not have chosen an initiate of magical arts as his physician. In 1317 the Inquisition of Tarragona condemned his books to be burned, but this was for the heretical sentiments which they contained. He wrote strictures on the monastic state and the service of religion, and maintained that works of divine faith and charity were more agreeable to God than the Sacrifice of the Mass. His skill in Hermetic philosophy has been generally recognised. His contemporary, the celebrated Jurisconsult, John Andre, says of him:--“In this time appeared Arnold de Villeneuve, a great theologian, a skilful physician, and wise alchymist, who made gold, which he submitted to all proofs.” Arnold has also the character of writing with more light and clearness than the other philosophers. His alchemical works were published in 1509, in one folio volume. His _Libellus de Somniorum Interpretatione et Somnia Danielis_ is excessively rare in its original quarto edition. Several alchemical and magical works are gratuitously ascribed to him. Among these must be classed the book called _De Physicis Ligaturis_, supposed to be translated from the Arabic--_De Sigillis duodecim Signorum_, which is concerned with the zodiacal signs--and the book of the “Three Impostors,” which the _Dictionnaire des Sciences Occultes_ denominates “stupid and infamous.” The _Thesaurus Thesaurorum_ and the _Rosarium Philosophorum_, the _Speculum Alchemiæ_ and the _Perfectum Magisterium_, are the most notable of all his alchemical treatises. To these the student should add his _Scientia Scientiæ_ and brief _Testamentum_. The editions are various, but the tracts will be found in collected form in the _Bibliotheca Chemicæ Curiosa_ of J. J. Mangetus.