||The contribution of Jesuits to the different fields of knowledge, including philosophy, is historically well known. In fact, since the foundation of the Society of Jesus, in the 16th century, Jesuits from different generations and cultures have taken part in the philosophical debates of their time and their different contexts. Since the foundation of the Society of Jesus, in 1540, the Jesuits, individually and as a body, have engaged in a fruitful dialogue between the Christian tradition and different dimensions of human culture. During almost five centuries, numerous Jesuits taught philosophy in academic institutions all over the world. Some of them have their names recorded in the history of philosophy. Of course, the majority of them is not anymore remembered, despite their valuable contribution to the development of the Jesuit intellectual tradition up to our times. In fact, as an heir of the Roman College, the first academic institution founded by the Society of Jesus, in 1551, the Pontifical Gregorian University, in Rome, is a witness to this tradition, which has been kept alive thanks to the discrete work of both Jesuits and lay intellectuals. Known as the University of the Nations, this institution corroborates not only the capacity of the Jesuit tradition to put faith in dialogue with reason, but also the option to take the concrete reality of each human culture and its historical context as its point of departure. The Jesuits’ willingness to engage in dialogue with different intellectual perspectives is underpinned by one of the most defining traits of the Jesuit charism, namely, the conviction that God can be found and served in all things. Accordingly, Jesuits have adopted, from the beginning, an amenable stance towards the world with its different cultures and intellectual trends. As such, Jesuits have, since the beginning, inhabited the frontiers of human thought. According to the contemporary philosopher Paul Gilbert, SJ, within the institutions under the leadership of the Society of Jesus, it was always possible to maintain an equilibrium between two principles: “intellectual unity” and “openness to the world.” Without detriment to the Jesuit identity, the companions of Ignatius have been willing to dwell in the various dimensions of human reality, in their multiplicity and plurality. Either in the renewal of Aristotle’s and Aquinas’ metaphysics, or in the dialogue with modern philosophers such as Descartes, Kant, or Hegel, and even in the inculturation in non-European contexts, the Jesuits have been able to preserve the Christian tradition through an original development of human culture in all its richness and diversity. With respect to the last century, it has to be acknowledged that a significant number of Jesuits made significant contributions, with recognized competence, to philosophy. Certainly, the 20th century was particularly complex in many respects. It would be enough to recall that this period, which brought with it unprecedented social, scientific, and technological developments, was also the stage for the two World Wars. With the emergence or consolidation of philosophical currents such as Marxism, Phenomenology, Existentialism, Structuralism, and Post-Modernism, the past century was, without any doubt, fascinating from the intellectual point of view. Jesuits such as Karl Rahner, Frederick Copleston, Bernard Lonergan, William Norris Clarke, John F. Kavanaugh, Teilhard de Chardin, Gaston Fessard, Jean Daniélou, Henri de Lubac, Michel de Certeau, Xavier Tilliette, Paul Valadier, Paweł Siwek, Ignacio Ellacuría, Francisco Taborda, Henrique de Lima Vaz and, in the Portuguese context, Diamantino Martins or Júlio Fragata, among many others, were able to engage different philosophical currents, problems and controversies of their times. Faithful to their long tradition of being present in the frontiers of thought, those Jesuits have engaged in a fruitful dialogue with these intellectual trends, offering relevant contributions to different ongoing debates. Within this context, the present volume recalls and discusses the philosophical contribution of some of the most prominent Jesuit protagonists of the intellectual interchange that took place in the 20th century. This volume also intends to celebrate the 75th anniversary of the Revista Portuguesa de Filosofia, which happens just before the inauguration of the Ignatian Year. Decreed by Father Arturo Sosa, the Superior General of the Society of Jesus, this celebratory Year will start on May 20, 2021, precisely 500 years after Ignatius of Loyola, the founder of the Jesuit Order, was wounded at the battle of Pamplona. We are happy that this volume could bring together outstanding specialists in the thought of some of the most prominent Jesuits philosophers of the last century, namely Paul Valadier, Paul Gilbert, Józef Bremer, Jacek Poznański, Alexander Maar, Patrick H. Byrne, M. Ross Romero, Carlos Alvarez, Hélio Pereira Lima, José Gama, Domingos Terra, Gabriel Flynn, Marie-Gabrielle Lemaire, José Sols Lucia, Lorena Zuchel Lovera, Pedro Pablo Achondo Moya, Enzo Solari, Massimo Borghesi, Mendo Castro Henriques, João Barbosa, and Dominique Lambert. In addition, in the celebration of the 100th anniversary of Júlio Fragata’s birth, Maria Teresa Fragata presents a memory of his life and thought. We hope that this volume may be useful to all those interested in the Jesuit philosophical tradition. Hopefully, it will stimulate scholars to pursue a fruitful and creative dialogue with contemporary philosophy, in the footsteps of the Jesuit philosophers featured here. We would like to thank all the authors and all those who, in different ways, made this volume possible.