The beginning of Chiara Lubich's journey with the Focolare Movement she founded was marked by a period of intense illumination, analogies of which can be found in the history of some of the great charisms and spiritual movements that have risen up in the Church throughout the centuries. This period of special graces is now the object of study of an interdisciplinary study group called "Abba School." Its aim is to unfold the doctrine and the potential contribution to contemporary culture implicit in the Focolare's spirituality. An Introduction to the Abba School collects some of the first-fruits of this study: a talk by Focolare foundress Chiara Lubich on the principal cornerstones of a Theology and Philosophy of Unity; an introduction to an original methodology of theology that derives from the Abba School (Piero Coda, professor of fundamental theology at the Lateran University in Rome); an interpretation of the mystical experience lived by Chiara Lubich (Gerard Rosse, a prominent French Bible scholar); a glimpse of the reverse side of unity, that is, some incisive ideas on the reality of hell (Hubertus Blaumeiser, professor at the Gregorian University in Rome), and a talk centered on Jesus forsaken, a key element of the spirituality of the Focolare (Giuseppe M. Zanghi, editor-in-chief of the Nuova Umanità review).