Faith, Reason, and Christian Philosophy: Leo XIII

This Dispatch will delve into Pope Leo XIII's groundbreaking encyclical Aeterni Patris from 1874, which laid the foundation for his pontificate, including the famous encyclical Rerum Novarum of 1891. It also opened new ways for doing Christian Philosophy within the Church.

In 1874, Pope Leo XIII addressed the question of the relevance of philosophy to the life of the Church. It provided the political-theological foundation for his pontificate, especially for the more famous social encyclical Rerum Novarum (1891).

“Philosophy, if rightly made use of by the wise, in a certain way tends to smooth and fortify the road to true faith, and to prepare the souls of its disciples for the fit reception of revelation; for which reason it is well called by ancient writers sometimes a steppingstone to the Christian faith, sometimes the prelude and help of Christianity, sometimes the Gospel teacher.”

Pope Leo XIII, Aeterni Patris, 1874

Aeterni Patris was much more than a pious encyclical aiming to improve the formation of future theologians and clergy. It was part of a pontifical political program to restore the church's voice in society. It would provide the basis for a series of encyclicals in which Pope Leo XIII set out a new theory and practice for catholic engagement with the modern world.

Pope Leo XIII was the first modern Pope to understand the positive impact that philosophy could make in supporting the public vocation of the church in the world.  

The Pope presents three key political reasons for the Church's engagement with philosophy, particularly that of Aquinas. Firstly, he argues that every believer should be able to provide a rational basis for their faith (1 Peter 3:15), although faith should remain the ultimate foundation. Secondly, amidst the political complexities and fragmentation of public discourse at the time, there arose a need for a comprehensive worldview, one that Aquinas' works seemed to offer. Lastly, Pope Leo XIII contends that Aquinas equips the Church to discuss the fundamental aspects of political authority, laws, government, and mutual charity to preserve the true essence of liberty in the public square.

While some have argued that the social encyclical Rerum Novarum was merely coincidental, it becomes evident, when examined within the broader political, philosophical, and theological program of Pope Leo XIII, that it was an integral component. The legacy of Pope Leo XIII's positive view of philosophy would resurface 120 years later in Pope John Paul II's thought-provoking encyclical Fides et Ratio, published in 1998

Finally, the ghostwriter, or main editor, for Aeterni Patris and Rerum Novarum was the Dominican friar Tommaso Maria Zigliara OP (1833-1893). Zigliara taught at the Collegium Divi Thomae, the future Pontifical University of Saint Thomas Aquinas, Angelicum. He was created cardinal by Pope Leo XIII on the 12^th of May 1879, together with another hero of mine: John Henry Newman.