Christina (or Kristina) of Sweden is really as much a philosopher who just happened to rule a country for a while as a ruler. She was born in 1626 to King Gustav II; her mother was disappointed that she wasn't a boy, but her father made sure she had exactly the training and education that a boy prince would have had. Gustav was killed in battle in 1632, and Kristina was crowned (her title was actually the equivalent of "king"; only the wife of a king was called "queen" in Sweden), though it would be 1640 before she actually started participating in government. She was re-crowned at the age of 18, and started to come into conflict with her father's former chancellor, Axel Oxenstierna, because Christina was dedicated to ending the Thirty Years' War while Oxenstierna was unwilling to compromise Sweden's desires of getting something out of the fighting. It would take until 1648, but Christina was a major force in ending the war.

In 1645, she helped in founding Sweden's first newspaper. The next year, she began a correspondence with Rene Descartes, and gradually started to gather scholars to her court. In 1650, Descartes himself came to Sweden, where he contracted the pneumonia that killed him.

Over the next few years, Christina began secret correspondence with a group of Jesuit scholars, confessing her skepticism in the Lutheran religion she was brought up in. Roman Catholicism was illegal in Sweden at the time; Christina's own father had started out tolerant but grown into a Catholic-hater. She had a nervous breakdown in 1652. By June 1654, the solution became firm in her mind; she announced that she was abdicating the throne of Sweden in favor of her cousin Charles. Legend says she took the crown from her own head, as no one else at court would do it, and put it on Charles. Her words at the time of the abdication:

"I say this explicitly, that it is impossible for me to marry. That is the way it is for me. The reasons for this I will not tell. I have frequently prayed to God, that I shall get that mind, but I have not been able to get it...My temper is a mortal enemy to this horrible yoke {marriage}, which I would not accept, even if I thus would become the ruler of the world. Which crime has the female sex committed to be sentenced to the harsh necessity which consists of being locked up all life either as a prisoner or a slave? I call the nuns prisoners and the married women slaves."

After abdicating, she left Sweden and went to Rome. In 1655 she publicly converted to Catholicism. Pope Alexander VII received her and gave her a place to live, but she did not work well with the strict atmosphere of piety; many say she was still a skeptic underneath. She was short on money and missed having power, perhaps; in any case, she made plans to seize the city of Naples/Napoli from Spain. Trying to raise support in France, she found that one of her servants had told the Pope of her plans, and she had that servant murdered (after having Catholic last rites given to him). Public opinion turned against her for this.

While studying astronomy, she also visited Sweden and tried to gain support in becoming Queen of Poland, but this didn't work out. She returned to Rome, had an astronomical observatory added to her palace, and started working on the letters that would be compiled into her book of philosophical Maxims. She was a patron of the theater, opera, her sculptor friend Giovanni Bernini, and published letters urging religous tolerance of French Hugenots and the Jews of Rome. She started an autobiography, which was unfinished at her death in 1689 but was eventually published posthumously. To quote her Maxims, "The soul has no gender."

Burke, James. "The Buck Stops Here." Scientific American, October 1997.