Short answers, pulled from the story.
The Protestant Ethic and the Spirit of Capitalism is a work by German sociologist Max Weber arguing that Calvinist and other Protestant religious ideas shaped the development of modern capitalism in Northern Europe. Weber contended that the Protestant doctrine of a divine calling in secular work, combined with prohibitions against luxury spending, pushed believers toward systematic hard work and investment of accumulated wealth.
Max Weber composed the original German text in 1904 and 1905, first as a series of essays. American sociologist Talcott Parsons translated the work into English for the first time in 1930.
In 1998, the International Sociological Association listed The Protestant Ethic and the Spirit of Capitalism as the fourth most important sociological book of the twentieth century, ranking behind Weber's own Economy and Society, C. Wright Mills' The Sociological Imagination, and Robert K. Merton's Social Theory and Social Structure.
Weber used the iron cage to describe the condition of modern workers trapped in mechanized industry after the religious motivations behind capitalism had faded. Drawing on Richard Baxter's image of worldly goods as a light cloak the saint could cast aside at any moment, Weber argued that fate had turned that cloak into an iron cage. The passage appears on page 181 of the 1953 Scribner's edition.
Critics have challenged both the empirical foundation and the historical sequencing of Weber's argument. Historian Fernand Braudel argued that capitalism originated in Mediterranean trading cities before the Protestant Reformation, and that northern European centers simply copied earlier Italian and Dutch models. A 2015 study by Davide Cantoni found no effects of Protestantism on economic growth in German cities over the period 1300-1900.
The Protestant Ethic is widely read as a challenge to Karl Marx's historical materialism, which held that religion and other institutions are built on economic foundations. Weber inverted this by arguing that a religious movement, Calvinist Protestantism, helped generate capitalism. Weber himself resisted a purely idealist reading, writing that his aim was not to substitute a one-sided spiritualistic interpretation for a one-sided materialistic one.