The landscape of Europe in the Middle Ages was seeing a major shift. The barter system was predominant for centuries, this means, trading one good for another. When Europe switched to a 'money economy', the Church started to use it as a tangible way to quantify a person's human worth.
This couldn't have been possible without a tangible currency system. However this later caused people to question the logic behind this system.
Quick fact: The church even started selling indulgences for dead people!
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