The history of contemporary Catholic Social Teaching spans over one hundred years and five Popes.  Although the times urged each one to address social conditions, they did so not with the intention of making a seamless corpus of documents, but rather to address the concerns of that time within the context of their predecessors.  Although there is no explicit mode of analysis by which each one contributed to the teachings and principals of Catholic Social Teaching, it is possible to derive some general method in their thought.  I believe this is possible because all of the authors were working, in general, from a common theological and philosophical framework: the thought of Thomas Aquinas.

Pope Leo XIII (1873-1903) was basically a conservative thinker.  One problem he faced in his pontificate was a dizzying array of philosophical schools of thought in society and in the church.  It made public discourse difficult.  As a younger man he had been introduced to Thomism (refers to Thomas Aquinas) and found it to be centrist enough to serve the church well.  

Aquinas [1220-1274] had taken the pagan Greek thought of Aristotle and was able to link Christian tenets to it without fracturing the philosophy.  This was nothing new, after all, Christian thinkers of the first five centuries had used Platonism to explain the faith (e.g, Augustine).  Aristotle’s ‘realism’ differed from the idealism of Plato, in part because he had a scientific bent: his biological observations were astute.  Hence, there was an attractive affinity between reasonable rationalism and the experience of faith in the world.  Aquinas’s synthesis was genius, but his writings were not universally accepted, at least not until Pope Leo XIII ‘enthroned’ them as the method for the Church to do theology (1879, Aeternis Patri).  As a result, all seminaries and scholars were schooled in Thomism.  

What of Thomism emerges as common principals from this corpus of Catholic Social teaching?  The most prominent principal is Natural Law.  Since reason is a God-given attribute to humans, the ability to discover and arrange in accord with reason is a good.  Natural Law is that ingrained truth of things in themselves that can be apprehended by reason; this truth does not require divine revelation.  Within the realm of Natural Law are principals the right to private ownership of property, to act in a free manner, the essential quality of the common good (that which supersedes individual good in scope), and rights and responsibilities.  

Justice is part of the natural law.  Although justice is a human edifice, it is in line with human dignity, respect, mutual good, and distribution of resources.  The Popes drew heavily from justice to describe what is not working in the troubled social conditions of their times.  

Another key trait in the encyclicals from Thomism is virtue.  Humans are attracted to the good, and a practical manifestation of the good is in right acting which, as a habitual form of acting, is called virtue.  Hence, virtues of fairness, magnanimity, honesty, working, self-respect and the like are a basis of the papal social commentary.  

The social encyclicals add a dimension after Vatican II (196201965), that of Scripture/ Revelation.  Revelation does not replace reason but it expands it for the Christian.  The demands and motive of acting presented by revelation supersede just reasonability; revelation points us toward the salvific demands of discipleship in Christ.  Still, the non-Christian can read these encyclicals and derive many worthwhile social comments.  For the Christian, there is more involved than a good world order; there is embodying the love of Christ for one and for all.