To answer the question “How would a modern democratic system affect how a medieval society functioned?”, we need to learn the specific definition of democracy. Here is a quote from a Stanford University lecture about the 4 main elements of democracy:
The 4 main elements needed for a democratic society:
1. A political system for choosing and replacing the government through free and fair elections.
2. The active participation of the people, as citizens, in politics and civic life.
3. Protection of the human rights of all citizens.
4. A rule of law, in which the laws and procedures apply equally to all citizens.
The feudal system in place in the Middle Ages would need to be changed heavily to even slightly resemble the elements of a democratic society, which would lead to a major change in the culture and events of the Middle Ages.
The balance of power would be very different with democracy as the form of government. I think that without the tiers of the feudal system, there would be really only 3 levels of people, much like today - the poor, the middle class, and the rich. This may be similar to the feudal system, but it differs with the fact that people could change classes, instead of being fixed to whatever class you were born into. I think that generally, there would be much less of a hierarchy, and instead, people would be much more equal. There would still be the main leader of a country, but he/she would be democratically elected by the people. I think that with time, the society would progress to having elected representatives for districts, much like the democratic system today.
I think that the class of peasants would become the poorer people of the society. Instead of being ruled by a lord, I think that the poor would own land that they would farm on. They would have much more freedom and the potential to increase their wealth and status. I think that they would remain more agriculturally based, staying self sustained with their own farm. The life of the poor would still be pretty hard, but I think that without the added pressure of a lord, they would do a lot better for themselves, maybe producing enough crops to sell and increase their wealth.
I think that in this society, nobles would not exist, but instead there would be the rich. Like nobles, they would live in much better residences than most of the population. Instead of being self sustained like the poorer class, I think that this class would buy goods and supplies, instead of producing their own. Compared to the feudal system, the power gap between the poor and the rich would be much smaller, meaning that the rich in this democratic society would have much less influence than those in the feudal system.
I think that without the hierarchy power of the feudal system, interaction between people would be much different. I think that the idea of capitalism would be more widespread, and power would be much more balanced overall. With a more modern governance system, I would assume that advances in society and science and technology would happen much faster. I think that people would begin to have the time, money and energy to put more effort into education and research, leading to many more innovations.
I think more people would move into towns and cities faster, and that trade and economic growth both inside and outside of towns would be much greater than in the feudal system. The poor and rich alike could choose what they wanted to do and where they wanted to go.
In short, many social and ecomnomic benefits would apply to all classes of people, especially the poor.
I think that with a democratic governance system, the power of the church would be undermined, as the leaders would do what would please the people, instead of just following what the church said. This would lead to changes in major events, such as the crusades. Also, assuming that the democratic system lead to a more rapid development of science and technology, the world today could be vastly different. Perhaps we would be a much more advanced society.