This document discusses key events and figures related to the development of Christianity and Catholic social teachings. It covers Constantine's Edict of Milan which legalized Christianity in the Roman Empire, the French Revolution which led to secularization, the Industrial Revolution which dehumanized workers, and Karl Marx and his communist ideas. It also outlines the major Catholic social encyclicals starting with Rerum Novarum in 1891 addressing the role of the church in society and workers' rights in response to the Industrial Revolution.