What (if anything) makes political parties indispensable?

It is received wisdom in political science that parties are indispensable in a large-scale democracy. However, one might think that this belief reflects path dependency or a lack of imagination of alternative democratic systems. The recent theoretical development of new alternatives to traditional forms of representative government such as lottocracy or liquid democracy therefore offers an ideal context for questioning the assumption more thoroughly. The functions usually performed by parties are well-known, but it is less clear which of them could not be taken up by a different institution or body under an alternative arrangement. What would be the deep normative reasons to preserve the party form even in a completely reformed democracy? This is the question addressed in this article by bringing together recent pieces of literature on democratic innovations and the political theory of political parties. We argue that parties allow to mobilise and politicise citizens around a positive ideology, make it easier for citizens to follow political processes, thereby facilitating popular control and accountability, and give more visibility and strength to the opposition. These extremely valuable functions should be put in the balance with their flaws and with the benefits of alternative democratic systems.