Petri's book on Aquinas and Pope John Paul's Theology of the Body is Volume 7 in the Thomistic Ressourcement Series from the Catholic University of America Press. The purpose of this series of books is to demonstrate that the wisdom of Aquinas remains relevant for contemporary thinking. In keeping with the aim of the series Petri shows that Pope John Paul is significantly influenced by Thomism. However, Petri is also aware that some commentators interpret the Theology of the Body solely on its own terms and indeed regard the Pope's catechesis as something of an innovation. Petri's aim then is not merely to rediscover the wisdom of Aquinas. It is also to relocate the hugely popular work of Pope John Paul in the Thomistic tradition. As Petri explains an authentic understanding of the theology of the body relies on an appreciation of the intersection of the thought of Pope John Paul and Aquinas. The book makes an important contribution to the growing body of literature on the Pope's catechesis.
The notion that Pope John Paul's Theology of the Body is a major shift away from the tradition is perhaps fuelled by discussion on the Pope's interest in phenomenology and his particular understanding of personalism. However this notion of a shift may also be related to the Catholic moral tradition. In order to resituate the Pope's thinking in Thomism, Petri convincingly argues that the Pope's personalist writings, including his early work in moral theory, are written in response to the manualist tradition rather than to Aquinas. Petri's book therefore begins with a general outline of what he sees as the historical discontinuity between the moral theology of Aquinas and that of the manualists. This first chapter should not come as a surprise to anyone interested in the development of moral theology and, as Petri acknowledges, the chapter follows the same line of thinking as that of Servais Pinckaers. As such it is perhaps subject to the same critique due to any view that uncritically asserts that the fourteenth century precipitated merely a downward spiral in moral theology: Alphonsus Liguori, who wrote one of the early moral manuals for members of his religious congregation, is after all the patron saint of moral theology. Nevertheless, Petri usefully points out this development specifically in relation to the writings of Pope John Paul.
Having described the moral manuals as essentially concerned with sin, cases of conscience and an evaluation of isolated physical acts rather than beatitude and a growth in virtue, in his second chapter Petri presents twentieth century personalism as a response to the perceived physicalism of the moral manuals. Since this is in the specific context of marriage and contraception, Petri offers a comprehensive and thorough overview of the debates leading up to Pope Paul VI's encyclical, Humanae vitae. Petri understands the birth control debates to be the result of the previously outlined problematic moral theology that tended to overemphasise the exterior structure of human action to the detriment of a unified view of the human person.
There are of course personalisms rather than simply personalism and Petri does touch upon some different strands of the personalist understanding of marriage. However he does not detail some of the serious concerns with some personalist approaches notably approaches that place the person at the centre of everything. Certainly Pope John Paul consciously avoids such an approach, but it is one that sometimes seems to surface with some interpretations of the Pope's theology of the body. Petri ends this second chapter by arguing that the need to defend the conclusions of Humanae vitae from charges of physicalism was decisive in the development of Wojtyła's personalist philosophy, a philosophy that also respects the natural law. Wojtyła's personalism then is set within his larger project of turning to subjective experience and reconnecting experience to theology.
In the following six chapters Petri sets out three chapters devoted to Karol Wojtyła/Pope John Paul and, mirroring these, three to Thomas Aquinas. To begin with Petri details Wojtyła's early moral theology before he became pope where, from a foundation in Thomism, Wojtyła engages with the subjectivity of the person and with phenomenology through the thought of Max Scheler. Then Petri examines Wojtyła's ethics of sexuality as a practical application of Wojtyła's general moral theory. This leads into an analysis of what Petri regards as a major theme of the Pope's catechesis, the spousal meaning of the body that expresses the gift of self for all human beings whether married or not. Key elements in these chapters are given prominence in the subsequent three chapters on Aquinas. Petri begins with the anthropology of Aquinas in order to distance this from the apparent physicalism of the manualists and to indicate initial steps towards complementarity between the sexes and the stirrings of the incommunicability of persons as developed by Pope John Paul. Petri's analysis of the movement of love in the Summa Theologiae becomes foundational for Pope John Paul's spousal meaning of the body as a gift of the self that leads to complete fulfilment of self. This is followed by an examination of Aquinas's understanding of marriage and the conjugal act that, Petri argues, need not be interpreted in a strictly physicalist way. Certainly Petri has to deal with some difficult questions on Thomas's perspective on women and he manages the discussion well.
In his concluding chapter highlighting some points of comparison and necessary development Petri expresses the hope that he has succeeded in showing how the thinking of Aquinas and Pope John Paul can be mutually enriching. This he certainly has done. However, even though Petri states that it is beyond the scope of his study to determine whether Thomism can be incorporated into phenomenology, it seems that his book has covered enough ground to invite further comment on this question.
Petri's aim in part has been to establish that although Wojtyła explores subjective experience through phenomenological analysis, Wojtyła never renounces metaphysical or ontological categories. Indeed Wojtyła recognises that the scholasticism of his seminarian studies needs to be supplemented by a more subjective approach. According to Petri, Wojtyła presumes certain ontological conclusions and this is why an appreciation of Aquinas is necessary for a full understanding of Wojtyła's thought and his later theology of the body.