At the heart of this book is what would appear to be a striking and fundamental paradox: the espousal of a ‘scientific’ doctrine that sought to eliminate ‘dysgenics’ and champion the ‘fit’ as a means of ‘race’ survival by a political and social movement that ostensibly believed in the destruction of the state and the removal of all hierarchical relationships. What explains this reception of eugenics by anarchism? How was eugenics mobilised by anarchists as part of their struggle against capitalism and the state? What were the consequences of this overlap for both anarchism and eugenics as transnational movements?