After these two years at the Collège de Calvi, Lax transferred to the Collège de Montaigu, one of the leading theological colleges of Paris, where he studied under Maior but also was an important teacher at the College. One of Lax's fellow countrymen, who was also studying under Maior, wrote to the representative of the Spanish King in Paris:-
I am following the theology course of John Maior with great interest as he is a deeply knowledgeable man whose virtue is as great as his faith. ... may the eternal king deign to grant him long life that he may for long years be useful to our alma mater, the University of Paris.In 1517 Lax returned to teach again at the Collège de Calvi which he did for the next six years. These were years in which France was engaged in various wars and disputes particularly against Spain and its possessions. Charles I of Spain became the Holy Roman Emperor Charles V in 1519. Francis I had become king of France in 1515 and in that year he took Milan. Charles V visited Spain in 1522 and France felt threatened from all sides. Between 1521 and 1523 the French were expelled from Genoa and the area around Milan, but this led to a French counter attack in 1523. In that year foreigners were asked to leave the Collège de Calvi and shortly after this Lax decided to return to his native land. The conflict between Francis I of France and Holy Roman Emperor Charles V continued.
In 1524 Lax left France and returned to Spain. He was appointed professor at the University of Zaragoza and remained there for the rest of his life. He did achieve certain higher posts within the University of Zaragoza, eventually becoming Vice Chancellor and Rector.
Lax published several good mathematics books based on works by Boethius, Euclid, Jordanus and Campanus. He was one of the Spanish school of "calculatores" who studied mechanics, being particularly involved with numerical examples, and using as their main tools the elements of proportion theory and infinitesimal arithmetic. This school seems to have originated with Lax and other students of Maior who studied in Paris, then returned to Spain.
Lax was also known as a philosopher, often called the 'Prince of Sophists'. Almost certainly Maior's influence was one of the main reasons he studied logical subtleties. However, one of Lax's students wrote that he heard Lax express regret late in his career that he had spent so much time on 'such trivialities'.
Lax published Arithmetica speculativa (1515) which, according to the historian D E Smith, was:-
... a very prolix treatment of theoretical arithmetic based on Boethius and his medieval successors.Another work by Lax in the same year was Proportiones :-
... a more compact and formalistic treatment of ratios, with citations of Euclid, Jordanus and Campanus; unlike most sixteenth-century treatises on ratios, however, it does not deal with the velocities of motion in the Mertonian and Parisian traditions.He also published Quaestiones phisicales in 1527 but this text does not appear to have survived.
Article by: J J O'Connor and E F Robertson