What did Pope Leo XIII emphasize in his writings?

Pope Leo XIII is well-known for his significant contributions to social doctrine, particularly in regard to labor rights. His encyclical "Rerum Novarum," published in 1891, was groundbreaking as it addressed the conditions of the working class during the Industrial Revolution. He emphasized the dignity of labor, advocated for fair wages, and encouraged just working conditions. Leo XIII argued for the rights of workers to organize and form unions, asserting that a just society must look after the welfare of its most vulnerable members.

This focus on social justice and the rights of laborers marked a pivotal moment in Catholic social teaching, steering the Church's position on economic and social issues towards a more compassionate and equitable approach. It also laid the groundwork for subsequent Church teachings on social justice.

The other options, while relevant in various contexts, do not capture the essence of Leo XIII's most impactful contributions. His primary focus on labor rights reflects a momentous shift in the Church's engagement with social issues that continues to influence Catholic social teaching today.