The significance of money in society. Starting from Simmel's still underestimated "Philosophy of Money" as a social theory, through Keynesianism, to the latest contributions to monetary theory, the author outlines a theory of modernity that assigns money a key role not only in the realm of economics but also as a medium of socialization. However, money is presented not only as a medium but also as an "actor," a driving force behind societal modernization processes. This ambivalence is illustrated through the example of speculation and trust in money. The author succeeds in transforming historical theoretical questions into systematic ones, bridging the gap that has long separated sociology and economics to their mutual disadvantage.