Quote Originally Posted by Gelatinous Cube
It was a pretty simple concept, actually. You have a Heirarchy of lords. In return for allegiange to a lord that was "Higher up", the lesser ranking lords would recieve lands, but they would be expected to provide armies for the higher-ups when the time came.

That's putting it very simply, but it was a system based on a rigid social heirarchy, and a firm belief that your place in society is where you belong. It was more than a system, it was a mindset. A peasant was a peasant, a lord was a lord. Breaking that would throw the whole system away.

This system became unnecesarry when professional armies became the standard, and when the various aspects of the rennesaince challenged the idea of that Social Heirarchy.
Ok lets push a little deeper.

You're saying that a rigid social hierarchy is an essential element of feudalism. But where did the knights themselves come from? Most historians point to the fact that the first knights were from relatively low classes. Many of them might actually have been peasants. These made it up the social scale and in fact at one point their superiors began calling themselves knights as well. So how rigid was this social hierarchy?

Also, there are many other societies that have rigid social hierarchies that clearly were not feudal. A Roman patrician and a Roman slave had very different social status. The best a slave could hope for was to make it up the next rung and be a freeman. That was pretty rigid, no?

Finally, where do the townspeople and free farmers of Europe fit into the 'age of feudalism'? The communes in italy became independent states. Were they then not part of the system? How about the free people who owned allodial lands?