Europe's crisis of legitimacy stems from 'governing by rules and ruling by numbers' in the sovereign debt crisis, which played havoc with the eurozone economy while fueling political discontent. Using the lens of democratic theory, the book assesses the legitimacy of EU governing activities first in terms of their procedural quality ('throughput), ' by charting EU actors' different pathways to legitimacy, and then evaluates their policy effectiveness ('output') and political responsiveness ('input'). In addition to an engaging and distinctive analysis of Eurozone crisis governance and its impact on democratic legitimacy, the book offers a number of theoretical insights into the broader question of the functioning of the EU and supranational governance more generally. It concludes with proposals for how to remedy the EU's problems of legitimacy, reinvigorate its national democracies, and rethink its future.