text: Frederick also wrote philosophical works, publishing some of his writings under the title of The Works of a Sans-Souci Philosopher. Frederick corresponded with key French Enlightenment figures, including Voltaire, who at one point declared Frederick to be a philosopher-king, and the Marquis d'Argens, whom he appointed as Royal Chamberlain in 1742 and later as the Director of the Prussian Academy of Arts and Berlin State Opera. His openness to philosophy had its limits. He did not admire the encyclopédistes or the French intellectual avant-garde of his time, though he did shelter Rousseau from persecution for years. Once he ascended the Prussian throne, he found it increasingly difficult to apply the philosophical ideas of his youth to his role as king.
  Like many European rulers of the time who were influenced by the prestige of Louis XIV of France and his court, Frederick adopted French tastes and manners, though in Frederick's case, the extent of his Francophile tendencies might have been a reaction to the austerity of the family environment created by his father, who had a deep aversion for France and promoted an austere culture. He was educated by French tutors, and almost all the books in his library were written in French. French was Frederick's preferred language for speaking and writing, though he had to rely on proofreaders to correct his difficulties with spelling.