This is a book about European integration and mainstream parties of the left, the main underlying question driving it being: Given that the communist left was fatally wounded by the collapse of the Berlin Wall; given that, since then, the terms ‘left’ and ‘right’ have not infrequently been attacked (especially by populists) as being no longer useful for making sense of politics; given that social democracy, understood as ‘national Keynesianism’ no longer appears to be viable (as reflected in its long-term electoral decline), what does it mean to be on the left in the early 21st century and what can be done to revive its fortunes? Its answer is that being on the left means embracing principles of equality and international solidarity, and that since the nation state is too small to respond effectively to climate change and the other most pressing issues of the present, no viable strategy for left-wing revival in Europe can dispense with European integration as a central element, of which European democratisation is a core component.