Unlike the slightly older Masham, and most other Enlightenment philosophers, Mary Astell was not from a really rich family. She grew up in England. Like other girls in the 1600s AD, Astell never went to school, though her family spent most of their savings to send her younger brother to school.
When her parents died, Astell was 17 years old and had no money. She moved to London, where she knew some richer men and women who helped her. She couldn't get married because she had no dowry, and she never had children.
Astell published her first book in 1694, when she was 28 years old. She argued that contrary to what Aristotle had said, women were just as capable of reasoning logically as men. After all, Anne of Austria had just done a fine job ruling France. Astell objected to Hobbes and Locke's idea that men ruled families naturally because they were physically stronger. She pointed out that if strength was all that mattered, any criminal would be right to steal your wallet just because he had a gun. She suggested that mental strength - being smart - should count more for ruling than physical strength - being strong.
In her next book, Astell discussed people's relationship with God. While others were convinced that human love on Earth would lead people to love God, Astell saw human love as a distraction from loving God. Instead, she thought, education would bring people to a passion for God, and make them happy. But she thought you needed passion too - not just reason.
Even though Astell thought laws and rules that oppressed women were wrong, she stuck to her father's political ideas and supported the monarchy in England. Like Hobbes, Astell thought people needed one strong figure who would lead the country - she didn't care that by her time, Queen Mary and Queen Anne didn't really hold so much power anymore.
In 1712, when Astell was 46, she finally got to open a free school where poor girls could get the education she didn't get. The school was a success, and Astell ran it until she got sick with breast cancer. She was brave enough to have an operation to try to cure the cancer, even without anesthetic, but it didn't work. She died of breast cancer at 65.