An important milestone of 20th Century philosophy was the rise of personalism. After the crimes and atrocities against millions of human beings in two World Wars, especially the Second, some philosophers and other thinkers began to seek arguments showing the value of each human being, to expose and denounce the folly of political structures that violate the inalienable rights of the individual person. Karol Wojtyła appeals to the ancient concept of 'person' to emphasize the particular value of each human being. The person is unique because of their subjectivity by which they possesses an unrepeatable interior world in the history of humanity. Their rational nature grants them a special character among living beings, among which is the transcendence to the infinite. Wojtyła magisterially shows how each human being's personhood is rooted in a conscious and free subjectivity, which is marked also by personal and social responsibility. Wojtyła's original philosophical analysis takes for its starting point the human act, in which consciousness and experience consolidate voluntary choices, which are objectively efficacious. By their acts, the person determines their own personhood. This self-dominion manifests the person and enables them to live together in a community in which one's neighbor can be a companion on the voyage of life. This work provides a clear guide to Karol Wojtyła's principal philosophical work, Person and Act, rigorously analyzing the meaning that the author intended in his exposition. An important feature of the work is that the authors rely on the original Polish text, Osoba i czyn, as well as the best translations into Italian and Spanish, rather than on a flawed and sometimes misleading English edition of the work. Besides the analysis of Wojtyła's masterwork, this volume offers three chapters examining the impact of Wojtyła's anthropology on the relationship between faith and reason.