Similarities between Weber and Nietzsche
Both thinkers start from the idea that the reason for the problems of the consciousness (critical theory's mission) is found in our sensuous experience that has to do with power and domination. Moreover, Weber and Nietzsche also agree on the idea that modernity ushered in an era where we trade-off physical pain for mental pain.
Weber and capitalism
In Weber's view, capitalism is that it is the only viable system to structure a society. Yet, he cannot help but wonder whether we have lost something in the process of modernity and capitalism (a concept he often refers to as the loss of "magic" or disenchantment in the modern world).
Protestant ethic
The Protestant Ethic and the Spirit of Capitalism was written after a major nervous breakdown in Weber's life. He went from being an overwhelming supporter of capitalism and liberalism to siding with Nietzsche on the problems of modernity and capitalism.
Weber vs. Marx
Marx was a proponent of historical materialism, where you try to understand history by focusing solely on the material conditions of people living in a given period. In contrast, Weber moves towards a more complex notion of human motivation by including the values and traditions of a society.
Instead of using either materialism or idealism, he uses an interaction between the two variables which he calls elective affinity. For Weber, change happens when there are both proper institutions as well as proper ideas. A cautionary tale is that of twelfth-century China, where the institutions were fertile grounds for change, but the country was held back by the dominance of Taoist ideas (making the state of ideas less than "ideal").
Relation between wealth and religious status
Weber begins by highlighting evidence of a correlation between wealth and being a Protestant. The problem with his evidence is that there were other factors responsible for this relation that were not included in the analysis, thus making it impossible to draw a clear causal link between the two variables. To understand why that is, we have to look back at the nineteenth-century United States, where the class with the most wealth was known as WASP (White, Anglo-Saxon, Protestant). On average, the poor were Roman Catholic immigrants coming from places such as Ireland and Italy.
Spirit of capitalism
Another critical part of the book is Weber's investigation into the "spirit of capitalism," which he boils down to two essential components. The first component is the idea that greed becomes an ethical imperative (best way to behave morally) in capitalism, completing Marx's work by highlighting the true motivation of capitalists to accumulate capital. The second component is the rational economic calculation, where individuals are much more concerned with keeping track of inflows and outflows of capital than in any previous social system. Moreover, rational accounting is a component of the "spirit of capitalism" that appears long before the formal introduction of the capitalistic system.
Luther's concept of calling
The third important theme of The Protestant Ethic and the Spirit of Capitalism is Weber's inquiry into Luther's concept of calling and Calvin's idea of asceticism and predestination. Luther's notion of calling is the concept of having an occupation that served God through secular activities (replacing the passive life observed under the Catholic doctrine with that of the active life of the Protestant individual).
"You want to know whether you will go to heaven. Well there is one way to do it. Work hard, and if your work will be rewarded, this will be a sign that God loves you and you will go to heaven."
Calvin's concept of predestination
Calvinism introduced an essential idea to the Protestant ethic: that of predestination, which means that your faith (whether you go to heaven or hell) is decided at birth, and there is nothing that can be done by any priests (as it was the case with corrupt Roman Catholic priests who would take a bribe to comfort people about their place next to God in heaven). Paradoxically the concept of predestination helped worldly occupations flourish because it was the only medium through which you could get a peek at your destiny at the Gates of Heaven.