The title alerts us to two concepts that will ring bells for many readers of this review. In the subtitle we learn what the book's actual focus is: the role of Luigi Taparelli in the history of Catholic social thought. As a leading Jesuit writer for the Civiltà Cattolica from its founding in 1850 until his death in 1862, Taparelli (1793–1862) shaped the philosophical foundation that would characterize papal social encyclicals from Leo XIII's Rerum novarum (1891) through Pius XI's Quadragesimo Anno (1931) to the present. That is the thesis that the author seeks to demonstrate here.

Are there really no other contenders for this role? Is the notion of a single such influential thinker in the nineteenth-century church not farfetched? If Taparelli's role was as crucial as Behr makes it out to be, one would think it would be quite broadly acknowledged in the relevant literature. All the same, it seems that Taparelli's contribution to the foundations of modern Catholic social thought has been shunted to the margins. Behr's work aims to fill in this missing link.

Previous studies of Taparelli's thought are not numerous. One that stands out is by Robert Jacquin, simply titled Taparelli (P. Lethielleux, 1943; in the same year, Jacquin published his translations of some of Taparelli's Civiltà Cattolica articles). Behr has done a good job of scavenging the pertinent literature (see Bibliography, 233–245) for his chapters sketching the context of the post-Napoleonic Restorationist period and how “natural law” was regarded in intellectual circles. In chapters 3 and 4 he conducts a painstaking analysis of Taparelli's major work, a detailed “theory of natural law based on fact:” the Saggio teoretico di dritto naturale appoggiato sul fatto (Palermo, 1830–1843, revised in 1855 and republished in 1949 by the Civiltà Cattolica). Behr's conclusion (176–192) sums up that analysis and restates the case that Taparelli was the key theorist who laid the intellectual foundation for the relevant papal encyclicals of Leo XIII and Pius XI. He offers further documentation in his translations of the dense Italian within one of the Saggio's sections, dubbed a “Treatise on Subsidiarity” (201–231).

Taparelli's reasoning is based on his philosophical anthropology. Human beings are intelligent animals (reason). They can also make decisions (liberty) whether or not those decisions are based on right reason. They are also social animals, dependent on one another in many ways. All men and women have their rights, which must be respected (morality). Humans have needs too, which must be pursued (action): here are the roots of Taparelli's “natural law” theory and of rights, properly understood (145).

The modern rationalist understanding of natural law would seem to be very similar to this Thomistic one. What then made the two approaches philosophically so incompatible, apart from the obvious rivalries and hotly contested claims of the churchly and secular bodies? Taparelli's charge was that the rationalists failed to distinguish between abstract reasoning and reasoning in the concrete. This was a distinction he could not find specified in Thomistic thinking (147–149). Drawing this distinction, however, and consciously utilizing concrete reasoning opened the possibility for Taparelli to develop his own views of subsidiary groupings in society and state, with their own subsidiary (“hypotactical”) rights. Modern proposals for causes such as “popular sovereignty,” in Taparelli's estimation, seemed to overlook this critical distinction. He viewed any affinity in Catholic circles for political democracy as highly suspect and published his disdain in the Civiltà Cattolica, upsetting the more progressive element in those circles.

One reason why Rerum novarum hardly hints at Taparelli's intellectual legacy in particular may have been this inner-Catholic difference of opinion. After all, Vincenzo Pecci (since 1878 Pope Leo XIII), Taparelli's student in Rome back in the 1820s, looked upon these same, more democratically inclined Catholic leaders with growing favor in the years leading up to the encyclical. Nevertheless, Taparelli's Saggio left an enduring impression on Rerum novarum's drafters, including without doubt the pope himself.