Universalism is collapsing in real time. As Western hegemony wanes, the promise of universal values is unmasked as a parochial inheritance; and as AI systems multiply, universal truths transform into computed artifacts emerging from a particular code and training. In Concrete Universality, Lorenzo Marsili argues that the choice is not between a bankrupt universalism and an 'anything goes' relativism. He proposes a third path: universality as a practice of worldmaking. Drawing on Chinese philosophy, European thought and the contemporary metaphysics embedded in artificial intelligence and quantum mechanics, Marsili develops the concept of ontopoiesis: the idea that reality is not simply found but continuously produced through relations, cuts, and forms of mediation. This approach gives rise to a new political method. Universals are not timeless abstractions; they are fragile mortal achievements – concrete agreements and institutions that make the same thing visible to everyone, for a time, in a context. Marsili calls this 'concrete universality' – the formation of shared, binding practices that emerge from situated encounters yet gain planetary resonance, from nuclear regulation to digital ethics, from climate policy to cultural restitution. Here, universality is not a static ideal but an unfinished voyage whose horizons move as humanity moves. This book is an erudite and impassioned manifesto for a planetary philosophy – a way of weaving together a fragmenting planet, one universal at a time.