Simone Lucie Ernestine Marie Bertrand de Beauvoir ( or ; French pronunciation: [simon d@ bovwaR] ( listen); 9 January 1908 - 14 April 1986) was a French writer, intellectual, existentialist philosopher, political activist, feminist and social theorist. Though she did not consider herself a philosopher, she had a significant influence on both feminist existentialism and feminist theory. De Beauvoir wrote novels, essays, biographies, autobiography and monographs on philosophy, politics and social issues. She was known for her 1949 treatise The Second Sex, a detailed analysis of women's oppression and a foundational tract of contemporary feminism; and for her novels, including She Came to Stay and The Mandarins.

De Beauvoir was intellectually precocious, fuelled by her father's encouragement; he reportedly would boast, "Simone thinks like a man!" Because of her family's straitened circumstances, de Beauvoir could no longer rely on her dowry, and like other middle-class girls of her age, her marriage opportunities were put at risk. De Beauvoir took this opportunity to do what she always wanted to do while also taking steps to earn a living for herself.  After passing baccalaureate exams in mathematics and philosophy in 1925, she studied mathematics at the Institut Catholique de Paris and literature/languages at the Institut Sainte-Marie. She then studied philosophy at the Sorbonne and after completing her degree in 1928, she wrote her diplome d'etudes superieures (roughly equivalent to an MA thesis) on Leibniz for Leon Brunschvicg (the topic was "Le concept chez Leibniz" ["The Concept in Leibniz"]). De Beauvoir was only the ninth woman to have received a degree from the Sorbonne at the time, due to the fact that French women had only recently been allowed to join higher education.  De Beauvoir first worked with Maurice Merleau-Ponty and Claude Levi-Strauss, when all three completed their practice teaching requirements at the same secondary school. Although not officially enrolled, she sat in on courses at the Ecole Normale Superieure in preparation for the agregation in philosophy, a highly competitive postgraduate examination which serves as a national ranking of students. It was while studying for the agregation that she met Ecole Normale students Jean-Paul Sartre, Paul Nizan, and Rene Maheu (who gave her the lasting nickname "Castor", or beaver). The jury for the agregation narrowly awarded Sartre first place instead of de Beauvoir, who placed second and, at age 21, was the youngest person ever to pass the exam.  Writing of her youth in Memoirs of a Dutiful Daughter she said: "...my father's individualism and pagan ethical standards were in complete contrast to the rigidly moral conventionalism of my mother's teaching. This disequilibrium, which made my life a kind of endless disputation, is the main reason why I became an intellectual."

Using a quote from the above article, answer the following question: What did she write it on?
Leibniz for Leon Brunschvicg