Among modern political theorists, there are three contending conceptions of democracy: "aggregative democracy", "deliberative democracy", and "radical democracy". The theory of "aggregative democracy" claims that the aim of the democratic processes is to solicit citizens' preferences and aggregate them together to determine what social policies society should adopt. Therefore, proponents of this view hold that democratic participation should primarily focus on voting, where the policy with the most votes gets implemented. Different variants of aggregative democracy exist. Under "minimalism", democracy is a system of government in which citizens have given teams of political leaders the right to rule in periodic elections. According to this minimalist conception, citizens cannot and should not "rule" because, for example, on most issues, most of the time, they have no clear views or their views are not well-founded. Joseph Schumpeter articulated this view most famously in his book "Capitalism, Socialism, and Democracy". Contemporary proponents of minimalism include William H. Riker, Adam Przeworski, Richard Posner. According to the theory of direct democracy, on the other hand, citizens should vote directly, not through their representatives, on legislative proposals. Proponents of direct democracy offer varied reasons to support this view. Political activity can be valuable in itself, it socializes and educates citizens, and popular participation can check powerful elites. Most importantly, citizens do not rule themselves unless they directly decide laws and policies. Governments will tend to produce laws and policies that are close to the views of the median voter—with half to their left and the other half to their right. This is not a desirable outcome as it represents the action of self-interested and somewhat unaccountable political elites competing for votes. Anthony Downs suggests that ideological political parties are necessary to act as a mediating broker between individual and governments. Downs laid out this view in his 1957 book "An Economic Theory of Democracy". Robert A. Dahl argues that the fundamental democratic principle is that, when it comes to binding collective decisions, each person in a political community is entitled to have his/her interests be given equal consideration (not necessarily that all people are equally satisfied by the collective decision). He uses the term polyarchy to refer to societies in which there exists a certain set of institutions and procedures which are perceived as leading to such democracy. First and foremost among these institutions is the regular occurrence of free and open elections which are used to select representatives who then manage all or most of the public policy of the society. However, these polyarchic procedures may not create a full democracy if, for example, poverty prevents political participation.