The text describes the many wonders of Catalonia. Voltaire notes that it is one of the most fertile countries on earth and that it is very well located as it has many rivers, streams, and fountains. He proclaims that Barcelona is one of the beauties of Europe and that the country is designed to support the construction of ships. The mountains are filled with marble quarries, jasper ports, rock crystal, and many precious stones whilst the mines contain iron, tin, lead, alum, and vitriol. The eastern coast produces coral. Voltaire then turns to the people of Catalonia, claiming that they have not been made soft by abundance but rather have always been warriors. However, he notes, they have always been subjugated, having been conquered by the Romans, Goths, Vandals, and Saracens. Having shaken off the Saracens, Catalonia placed itself under the protection of Charlemagne. They then belonged to Aragon, and finally Austria under Philip IV. In 1640, they gave themselves to Louis XIII and retained their privileges but in 1652 returned to Austrian rule and sided with Archduke Charles against Philip V in the War of Succession.

In this letter, Frederick wishes that the “hot fever” of Europe would recover soon. He tells Voltaire that he himself is no longer sick in body or mind. The end of the letter turns political as Frederick addresses the Austrians directly, telling them that their ambition and their desire to dominate everything actually created more enemies for them, and that there will always be defenders of German and European liberties. This is probably a reference to the Seven Years War, which was fought from 1754-1763.

Voltaire writes that he has received d’Alembert’s letter dated 1 December and thanks him for his excellent work honouring the memory of du Marsais. He adds that he can never thank him enough for backing him up with his eloquence and reasoning as they say he did about the infamous murder of Servetus and the virute of tolerance in the Geneva article (which Voltaire notes he eagerly awaits). Voltaire then writes that wretches have tried to justify the assassination of Servetus and that these wretches are priests, though he admits that he has not read any of their works. One of these priests, whom Voltaire calls a rascal, asked the Council of Twenty-Five of Geneva for communication of the trial which, Voltaire writes, ‘will make Calvin forever execrable’ and the boarded viewed with contempt. He then asks d’Alembert who the other young priest is that wants to pass him off as a loan shark, questioning whether d’Alembert borrowed at usury from the Battle of Kollin, noting that d’Alembert had condessed that at the battle of the 5th everyone had to advance him money. Discussion then turns to war and Voltaire writes that the Austrians avenge and humiliate them terribly, noting that they have made thirteen attacks at the same time on the Prussian intrenchments, and that these attacks lasted six hours. He writes that ‘never was a victory more bloody and more horribly beautiful’, quipping that the French are more expeditious, completing their business in 5 minutes. Voltaire then discusses Frederick II, King of Prussia, remarking that Frederick always sends him verses, sometimes in despair and sometimes as a hero, and that he tries to be ‘a philosopher in my hermitage’ upon receiving them. He adds that Frederick achieved what he always wanted (to beat the French) but that the Austrians laugh at him. ‘Our shame of the 5 gave him glory’, Voltaire writes, ‘but he will have to be content with this passing glory, too easily purchased. He will lose his states with those he has taken.’ In response to d’Alembert’s suggestion that Voltaire writes a biography of Frederick II, Voltaire writes that Frederick will allow noone to write his story except for himself. Concluding the letter, Voltaire writes that there are aspects of the eulogy of du Marsais that will do great good as ‘it only takes five or six philosophers who agree to overthrow the colossus.’ He adds that he does not wish to prevent people from going to mass or hearing sermons but that it is ‘a question of snatching the fathers of families from the tyranny of imposters, and of inspiring the spirit of tolerance,’ noting that the ‘vine of truth’ has already been well cultivated by d’Alembert, Diderot, Bolingbroke, David Hume, etc. He ends by sending d’Alembert the good wishes of Marie-Louis Denis [née Mignot] [née Mignot] and asking if her ever sees the blind clairvoyant, charging d’Alembert with informing the clairvoyant that Voltaire is still very attached to her if so.