[citation needed] The family returned to France after the Edict of Saint-Germain in 1562, and settled at Crest in Dauphiné, where Arnaud Casaubon, Isaac's father, became minister of a Huguenot congregation.

Arnaud was away from home for long periods in the Calvinist camp, and the family regularly fled to the hills to hide from bands of armed Catholics who patrolled the country.

It was in a cave in the mountains of Dauphiné, after the St Bartholomew's Day's Massacre, that Isaac received his first lesson in Greek, based on Isocrates' Ad Demonicum.

At Geneva, Casaubon lacked example, encouragement and assistance and struggled against the troops of the Catholic dukes of Savoy, but became a consummate Greek and classical scholar.

Even though Henri Estienne, Theodore de Beza (rector of the university and professor of theology), and Jacques Lect (Lectius), were men of superior learning, they often had no time for Casaubon.

[2] Casaubon sought help by cultivating the acquaintance of foreign scholars, as Geneva, the metropolis of Calvinism, received a constant stream of visitors.

[3] In 1596, they succeeded, and Casaubon accepted a post at the University of Montpellier, with the titles of conseiller du roi (king's advisor) and professeur stipendié aux langues et bonnes lettres (salaried professor of languages and literatures).

From then on, he became the object of the hopes and fears of the two religions; the Catholics lavishing promises and plying him with arguments; the Protestant ministers insinuating that he was preparing to forsake a losing cause, and only haggling about his price.

Neither side could understand that Casaubon's reading of the church fathers led him to adopt an intermediate position between Genevan Calvinism and Ultramontanism.

When the king's sub-librarian Jean Gosselin died of extreme old age in 1604, Casaubon succeeded him, with a salary of 400 livres in addition to his pension.

Above all, he had ample facilities for using Greek books, both printed and in manuscript, the want of which he had felt painfully at Geneva and Montpellier, and which only Paris could supply at that time.

In Paris, Casaubon was still uneasy about his religion: the life of a Parisian Huguenot was always insecure, for the police were likely not strong enough to protect them against a sudden mob uprising.

On the other hand, the Huguenot theologians, especially Pierre du Moulin, chief pastor of the church of Paris, accused Casaubon of conceding too much, and of having departed already from the lines of strict Calvinistic orthodoxy.

Casaubon still retained his appointments in France, and his office as librarian: he had obtained leave of absence for the visit to England, where he was not supposed to settle permanently.

Lancelot Andrewes, then Bishop of Ely, also became Casaubon's friend, taking him to Cambridge, where he met with a most gratifying reception from the notabilities of the university.

[10] In 1613 he was taken to Oxford by Sir Henry Savile, where, amid the homage and feasting of which he was the object, his principal interest was for the manuscript treasures of the Bodleian Library.

[8] In 1614 he published De rebus sacris et ecclesiasticis exercitationes XVI which consisted of a philological analysis of the Corpus Hermeticum, a series of neo-platonic texts.

[11] He died in London of a congenital malformation of the bladder; but his end was hastened by an unhealthy life of over-study, and by his anxiety to acquit himself creditably in his criticism on Baronius.

The Exercitationes in Baronium are but a fragment of the massive criticism which he contemplated; it failed in presenting the uncritical character of Baronius's history, and had only a moderate success, even among Protestants.

[8] His analysis of the Corpus Hermeticum overturned the previous general opinion in Europe that these texts dated from almost the time of Moses by locating them between 200 and 300 AD.

[citation needed] His correspondence (in Latin) was finally collected by Theodorus Janssonius van Almeloveen (Rotterdam, 1709), who prefixed to the letters a careful biography of Casaubon.

[8] More recently, a complete edition of all the letters written by and to Casaubon during his stay in England was published with extensive cultural-historical notes and introduction (Geneva, 2018).

[8] Casaubon corresponded with scholars all over Europe, including Johannes van den Driesche and, more surprisingly, one of the doctors of the Ambrosiana Library and eminent historian of Milan, Giuseppe Ripamonti.

Ross King makes mention of Casaubon in his novel Ex-Libris, where he is said to have debunked the Corpus Hermeticum as a forgery (which he probably took from Frances Yates' Giordano Bruno and the Hermetic Tradition, published in 1964).