‘La perfection de l’acte créatif requiert de l’amour, et donc de la liberté’. Elisa Valero is an architect and a teacher. Her work, demanding and rigorous, is oriented towards the transmission of an architecture that is thought as much as built. This book, which reads like a manifesto, is a kind of first lesson in architecture. In La Théorie du diamant, the design of an architectural project and its implementation are equated to the work of cutting a diamond: both activities require a similar sensitivity, that combines creativeness with rigorous technical preparation. With simple and direct words, the lesson comes to us as a necessity to return to the fundamentals of the discipline. Nevertheless, her discourse is also totally addressed to her contemporaries: subjects such as the ethics of the profession, authenticity conceived as fidelity to the historical moment, the economy of means, sustainability and the limitation of losses in the choice of materials integrate the search for meaning that is specific to the profession of an architect. Through the analysis of certain spaces, especially living spaces. The beauty of those “diamond spaces” shows us how ordinary architecture can be the bearer of the essence of beauty. These “diamond spaces” derive from the precision with which space, light and other materials are used, all of which make them instinctively recognisable. In demonstrating her theory, Elisa Valero skillfully leads us to a climactic conclusion, with the notion of beauty becoming the ultimate goal of any architectural project.