MuMaGi is a self-authored culture: a cosmology, a language, a number and calendar system, and a set of working methods for making music and architecture. This book is its primary document, begun in 1999 and revised across nine editions. It is written from a position of erasure — through adoption, through the transatlantic slave trade, through ongoing colonialism and the soft violence of ubiquitous social conditioning — and from a sustained philosophical questioning of what reality is and who authors it. The question it puts is whether a person cut off from inherited culture can construct one deliberately, and what that would have to contain to be worth anything. And beyond that: to what extent are we all cut off from knowledge that would change the limits of what we perceive ourselves to be, and what we value. The book is organised into five parts, echoing its five core principles. The first examines how cultures are built and dismantled — memory, abstraction, emergence. The second sets out MuMaGi itself: the Joyo and Joya, Kyology, the eight dimensions, and dictionaries of terms, alphabet and calendar. The third and fourth turn to practice — the Circle of 12, the Fluid 15 rhythm, and the Oruko Clumpiset, a linguistic method for composition and improvisation. The fifth brings these together in Ar/T/khitecture and MuSound, where building and sound are treated as one discipline.