In his masterful book, Massa marks the fiftieth anniversary of the promulgation of Humanae Vitae (HV) by exploring the theological revolution of Natural Law (NL) models that arose in response to the encyclical's absolute condemnation of artificial contraception within the marital relationship. Part 1 presents a brief historical overview of how HV originated and how Richard McCormick convincingly demonstrated that it was fundamentally flawed in its normative conclusion because it relied on a flawed classicist, physicalist, neoscholastic NL model.

Part 2 draws extensively from Thomas Kuhn's classic text, The Structure of Scientific Revolutions, to explain the nature of paradigms or models and their role and function in revolutions. Kuhn's mantra is “reality is more complex than any model we can construct to explain it” (7); so also is theological reality. A model attempts to explain reality. Revolutions occur when, in a “period of crisis” (41), such as the communion church's response to the normative conclusion of HV, a model can no longer accommodate and adequately explain anomalies or inconsistencies between reality and the model. A new model, with fundamentally reconstructed terms, concepts, and structures, replaces it. Abandoning one model for another entails as much a comparison of the two models themselves as it does an analysis of each model's ability to explain reality (42).

Motivated by the crisis in the church caused by HV, Part 3 details the revolution of NL models by theologians in the United States. Charles Curran develops a “Postclassicist NL Paradigm” which, informed by historical consciousness and a personalist anthropology, proposes an alternative norm allowing for artificial contraception in marital relationships. Germain Grisez constructs a “New Natural Law” (NNL) model based on basic goods that are incommensurable and are known intuitively. One of these basic goods is marriage and its fulfillment through parenthood which, according to NNL, justifies HV's absolute prohibition of contraception. Jean Porter's model “Robust Realism,” which affirms an “essential continuity” between reason and nature, includes theological and other sources of knowledge, such as human laws, customs, and the sciences (132) to construct a model of NL that serves to order and interpret human experience (135). This ordering and interpreting reconstructs theological definitions of marriage and sexuality and justifies contraception and homosexual relationships. Lisa Sowle Cahill raises concerns that Porter's model sacrifices universality to ensure the particularity of a theological tradition; it is wedded to a Catholic theological understanding of nature and reason. She proposes an alternative functionalist, feminist, universalist NL model committed to the common good where moral truths emerge through culturally, historically, socially interactive conversations. Discernment of “revisable universals” emerge, they are not discovered, and they are open to evolution and development through the inductive, historically conscious methods.

Following Kuhn, Massa articulates two principles on competing models that seem to be in tension. On the one hand, to accept one model and reject another requires “the comparison of both paradigms with nature and with each other” (42, quoting Kuhn). On the other hand, the models are incommensurable, that is, scientists cannot determine which model is more true by simply comparing the models because each model may use the same terms and concepts, but those terms and concepts may have very different meanings (44) (e.g., basic goods). Massa espouses the incommensurability principle when considering the neoscholastic, Grisez, and Porter NL models and their interpretations of Aquinas. One cannot determine which model gets Aquinas “‘right’… because each one [is] ‘built’ on a very different Aquinas” (149). If one works deductively, from the model to its interpretations of Aquinas, this may be the case. However, if one works inductively, beginning with Aquinas, and then comparing Aquinas to each model's interpretation, one is able to make evaluative judgments on which model is a more accurate representation of Aquinas. The same holds true for the various models and the normative conclusions they reach on artificial contraception. If one begins deductively with the models and moves to their normative conclusions, one cannot make a judgment about which model is more true because the normative conclusion logically follows from the model's premises. If, however, one begins inductively with the lived experience of married couples, the “nature” element that Kuhn lists as a basis for comparing models, one can certainly make an evaluative judgment on the model. Though Massa does not treat Pope Francis’ Amoris Laetitia, his Exhortation has followed such an inductive method, concluding normatively that natural methods of fertility regulation are to be “promoted,” not absolutely required as HV teaches. His normative conclusion and “New Pastoral Method” may indicate a revolution and embrace of one, or a combination, of the reconstructed NL models Massa explores.

Massa's book is written for an educated audience and is an invaluable resource for those who want to understand the impact of HV on moral theological discourse in the late twentieth and early twenty-first centuries.