Karl von Ketteler was a German bishop born on December 25, 1811, in Münster. He became the Bishop of Mainz in 1850 and was known for his progressive views on social issues. Ketteler advocated for the rights of workers and the poor, emphasizing the importance of social justice within the framework of Catholicism. Ketteler was also a key figure in the development of Catholic social teaching. He believed that the Church should address the challenges posed by industrialization and urbanization. His writings and speeches contributed to the foundation of modern social thought within the Church, influencing future discussions on social responsibility and ethics.