John P. Slattery is a senior research associate with the Dialogue on Science, Ethics, and Religion Program of the American Association for the Advancement of Science. Founded in 1995 by the AAAS, the program’s avowed purpose is to facilitate communication between scientific and religious communities. I met the author briefly in 2017 at a conference at Notre Dame devoted to the writings of Fr. Ernan McMullin, and at the time Slattery was keenly interested in an overlooked period of tension between the Vatican and Catholic scientists who were first coming to grips with Darwinian evolution at the end of the nineteenth century. As Slattery’s excellent new book reveals, this period is far more consequential for the checkered history of the Vatican’s relationship with science than the often-overhyped saga of Galileo and the Copernican Revolution.

Slattery’s book focuses on the career and fate of Fr. John P. Zahm (1851–1921), a priest of the Holy Cross at Notre Dame. Zahm’s initially cautious interest in Darwin’s work expanded into an enthusiastic embrace of the idea of biological evolution. This culminated in Zahm’s widely read 1896 book, Evolution and Dogma, in which he argued that the accumulated evidence of the biological evolution of species over the course of the planet’s history in no way presented a challenge to Catholic faith. Quite the contrary, as Zahm wrote:

My sole, ardent desire, has been to show that there is nothing in true science, nothing in Evolution, when properly understood, which is contrary to Scripture or Catholic teaching; that, on the contrary, when viewed in the light of Christian philosophy and theology, there is much in Evolution to admire, much that is ennobling and inspiring, much that illustrates and corroborates the truths of faith.

This was a message that had great appeal to many American Catholics at a time when the U.S. Church was in a period of confident expansion. Notre Dame owed much of its growing reputation as a major Catholic university to Zahm’s tireless efforts. As the university’s vice president he helped expand the school’s library and museum. As a teacher, he traveled around the country giving lectures about the importance of science for Catholics and the compatibility of science and faith.

But not everyone was as enthusiastic about evolution. The success of Evolution and Dogma brought Zahm into direct conflict with the Vatican’s Office of the Index of Prohibited Books, which in 1899 compelled Zahm to withdraw his book from circulation and to cease writing on the topic. These were humiliating demands, but Zahm agreed to them in order to avoid a public censure and keep his book from being placed on the Index. He spent the last two decades of his life traveling around the world and writing more broadly about science, but he never discussed evolution again.

To read Zahm today is to be astonished by the innocuous nature of his claims, and by the utter unwillingness of his critics to consider the scientific case for evolution. It’s worth recalling that when Zahm’s book appeared there was less support than there is now for Darwin’s theory that natural selection was the engine of evolution. This was before scientists knew anything about DNA, before there was any consensus on how traits were passed from one generation to the next (Mendel’s work had yet to be rediscovered). Since Zahm was one of those who dismissed natural selection, he was never really a Darwinist in the strict sense. The primary complaint of his critics was that he dared suggest Adam and Eve were not the result of a special act of creation but were, like all other living animals, the descendants of prior species—in this case, primates.   

But, as Slattery shows, Zahm’s critics were already predisposed to be hostile to any claim for evolution regardless of the scientific evidence in its favor, because their conservative theology was underpinned by a commitment to nineteenth-century Neo-Scholasticism. Slattery delves into the emergence of this movement and its key figures, including the Jesuit Joseph Kleutgen, who had a profound influence on Pope Pius IX’s Syllabus of Errors and his encyclical Dei filius, as well as on Pope Leo XIII’s encyclical Aeterni patris. These three papal documents all anchored reason in the scholastic tradition that grew out of the work of Aquinas.   

This tradition wasn’t a blanket adoption of Aquinas’s thought, but rather a new attempt to create an impregnable intellectual system, a form of theological rationalism that could resist all forms of innovation—in philosophy or science. As Slattery describes it:

First, the leaders of the Neo-Scholastic movement insisted on a singular philosophical structure for all Catholic scholarship that was both objective and universal, for doctrine could not exist in a world where the roots of philosophy were being forever debated. Second, the Scholastic interpretation of the philosophy of Aquinas was to be revered as the model of this universal structure, over against any philosophical systems based on Descartes, Kant, Locke, or anyone else in the modern world, as well as over against the theological interpretations of any other theologian, such as Augustine, Bonaventure, or Scotus. Third, Neo-Scholastics argued that by relying on Aquinas and other medieval philosophers, contemporary Catholic philosophy could be constructed as a single objective whole. Fourth and finally, Neo-Scholastics resisted anything resembling a historical approach to philosophical or theological development, for if doctrine could be changed over time, it would be impossible to test its veracity.

It’s difficult to overstate how much damage this bunker-mentality approach to philosophy and theology caused Catholic scholars over the ensuing decades, right up until the papacy of Pius XII when the Church finally accepted, albeit with reservations, the study of human evolution. The disconnect is beautifully demonstrated by a new translation of the Syllabus of Errors that Slattery provides in an appendix. The Syllabus laid the groundwork for Dei filius at the time of the First Vatican Council and established the narrow boundaries within which all Catholic scholarship was expected to proceed.

Slattery’s account of Zahm’s work provides a much-needed bridge between this reactionary era in the Church’s recent intellectual history and the more open era of Catholic thought that preceded the French Revolution (a period well described in Ulrich L. Lehner’s The Catholic Enlightenment). Faith and Science at Notre Dame is an indispensable addition to this history.

Faith and Science at Notre Dame: John Zahm, Evolution, and the Catholic Church
John P. Slattery
University of Notre Dame Press, $27, 292 pp.