The world is in disarray: social divisions, inequality, economic crisis, the climate catastrophe and the rise of a new authoritarianism all challenge the very foundations of civilization. Saying that capitalism offers no answers is not enough. We need effective alternatives, alternative experiments, more democracy, and socialist discussions. But there is another truth that is particularly evident amidst the Covid-19 pandemic: the challenges of a global world cannot be solved at the national level alone. Whether it is a matter of addressing the climate crisis, of the necessary restructuring of production methods, or of the worldwide fight for social justice: leftist forces in societies right around the world—in all their diversity, with their regional knowledge and experiences in local struggles for a better world—must rediscover internationalism and renew it from the bottom up.