The American system, for example, was intended to be a counterpoint to the supremacy expressed in European monarchism. Monarchy is based either on blood or "might makes right" - to take the mantle of king, you must be the first born son of the current monarch, or you much completely defeat them and take their throne.
This led to endless European wars.
People became horrified by the destruction of these wars and pondered how to stop them.
This became known as "the enlightenment".