René Descartes, the man considered as precursor of Scientific Method and author of revolutionary books such as his Discourse on Method, died in obscure circunstances that were not cleared out until recently.
In 1646, the impulsive Queen Kristina of Sweden, ethusiast of Arts and Philosophy (although not with deep thoughts, as Descartes himself admitted), started to write letters with the philosopher, who was at that time retired in Nederlands. Impressed by his teachings, she invited him to the Swedish Court as a guest to give her lessons on Mathematics and Philosophy. This was part of her plan to be surrounded by great European thinkers and transform Stockholm into a cultural centre.
After some forceful "invitations", for which the queen sent one of her admirals, and later even a warship, in 1649 Descartes reluctantly accepted her proposal. In Stockholm he was received with high honours, incorporated to the Swedish aristocracy, and granted conquered lands in Germany.
Death at the Court
He did not enjoy life in the court, however. Apart from some punctual jobs (such as some lines in French for a ballet, or plans for the Swedish Academy) he only had to teach the queen during the mornings. The problem is that Kristina got up extremely early, and scheduled their lessons at 5 in the morning in the middle of Swedish winter. This was very hard for Descartes, who was used to stay in bed reading and thinking until noon. He usually said, "men's thoughts freeze here in winter, same as water". Five months after his arrival, the 11th February 1650, he died.
The official version of the time was that he died of pneumonia. After treating the French ambassador in Stockholm, who had contracted this contagious illness, Descartes got also ill and died one week later. Considering he was not used to nordic cold, this seems plausible. He was buried in a cemetery for unbaptised kids (because he was a catholic in a protestant country), and some years later his remains were moved back to France. Closed case.
However, the French ambassador, Hector P. Chanut, graved this quote in his headstone: "he expiated his rivals' attacks with the innocency of his life". So, he could have been murdered. There was enough reasons actually, as he was a catholic with more influence than most nobles. He could have been considered dangerous and cause of the Queen's catholicist trends (who, four years later, abdicated, converted, and moved to Rome).
Proof of the lie
In 1980, by complete chance, the prove was found. The German scientific Eike Pies, reviewing letters from his ancestor Willem Piso at Leyden University (Nederlands), saw a letter sent to him by Johann van Wullen, personal doctor of Queen Kristina and witness of Descartes' agony. In that letter, the details on the symptoms are described day by day: weakening, vomits, diarrhoea, dizziness, skin's pigmentation, cutaneous damages, entheritis... symptoms commonly found in an Arsenic intoxication.
So, Descartes was almost certainly poisoned. How was the truth hidden? In the letter, Wullen points out that the Queen asked to read it before being sent, and ordered that it never fell in strange hands. Kristina probably wanted to save the prestige of Swedish monarchy, already target of rumours and palace intrigues because of the Queen's excentricities. This way, the murder was never investigated. And History books still tell the "official" version of the facts.