Across the world, socialism is undergoing an extraordinary revival. In America, candidates like Bernie Sanders and Alexandria Ocasio-Cortez have ridden to prominence on a wave of enthusiasm unthinkable even a few years ago. In England, Jeremy Corbyn has revitalized support among young people and speaks to crowds of thousands. And parts of Europe like Spain and Greece, the old political order has been overturned by new parties with socialist ideals. But what is socialism - and how does the political and philosophical theory that underpins it measure up against the versions we meet in the world around us? In Socialism, Professor Marc Stears guides