The use of her own body and self-portraits are key features in the work of Esther Ferrer. A member of the ZAJ group, which was central to Conceptual Art in Spain, Ferrer has become the most prominent performance artist in the country. She is committed to pursuing a classical approach and is fiercely independent. Her formalist leanings play a very important role in her photographic work, which includes this 2004 version of El libro de las cabezas, another addition to the series ‘Autorretrato en el tiempo’. In the series, which she has been working on since 1982, Ferrer uses self-portraits as a way to measure the passage of time and record the way her face changes as the years go by. The photographs in the series are taken from exactly the same viewpoint, with the same lighting, and in the same position. Ferrer cuts each image into two parts and combines the halves in different ways. This inevitably produces a single self-portrait that is recombined, altered and repeated over the years, without any substantial change in the subject. El libro de las cabezas also includes other parallel works by Ferrer, who has always used self-portraits in pieces that focus on social criticism and in purely formal exercises. In the images she stretches, condenses, distorts and alters her face based on mathematical methods, variable repetitions, and a set of ideas rooted in philosophy, music, and the reinterpretation of the world and its underlying causes. The use of her own face does not reflect any particular obsession on the part of the artist: to carry out her work Ferrer needed to have access to the same model over the course of decades and it would have been very difficult for her to depend on any other model in this way. This austerity of means and the logic of minimal cost are also evident in her performances. For decades this frugal approach has allowed her to maintain a degree of political and economic independence in accord with her social attitudes and principles. Time, repetition, the infinite and presence are the constituent elements of one of the essential oeuvres of contemporary art. Based on these core concepts, the artist constructs series of works that range from performance to installation, as well as ready-mades, photography, drawing and painting. This formal and conceptual freedom is what underpins the intellectual unity of her output—a quality rarely seen in such a varied body of work spanning so many years. Mathematics and musical rhythm, and the idea that all movement is repetition and that repetition only exists as versions—these are the key components of the existential philosophy that has defined Ferrer’s work throughout her career.