The notable philosopher who wrote extensively on ethics and existentialism is Simone de Beauvoir. A key figure in 20th-century philosophy, she challenged traditional views on gender roles and advocated for women's rights in her seminal book, The Second Sex. Beauvoir’s exploration of freedom and responsibility profoundly influenced existentialist thought. Her ideas on the constructed nature of gender and the importance of personal choice in defining one's identity resonated with feminist movements, marking her as a pivotal thinker in both philosophy and gender studies. Her legacy continues to shape contemporary discussions about feminism and ethics.