The correct answer is: "it violated the social contract principle, developed by Enlightenment philosophers".
Jean-Jacques Rousseau introduced the concept of social contract. It is the base of the claims for popular sovereignty during the Enlightenment era, as it established that citizens were the ones who held power legitimately, and these should grant it to representatives elected through suffrage, that would conform the goverments. Therefore, citizens had a say, indirectly, on the policies that the elected governors implemented in their countries.
This viewpoint sharply contrasted with the absolute monarchies that ruled in most European countries and on their colonies overseas. For example, the Stamp Act was implemented by a government that had not been elected by the citizens, in order to collect a certain amount of money from them that would not be used to their benefit.