Secondly, I also call them‘conciliar’popes because each, in turn, devoted
themselves to interpreting and consolidating the teachings of their respective
councils. Leo had to reconcile the conciliar documentDei Filius(1870), which
rather tersely but clearly affirmed the harmony of faith and reason, with
Quanta curaand itsSyllabus of Errors(1864). TheSyllabusconsisted of some
eighty erroneous propositions that had to be negated. The notorious eightieth
proposition is:‘The Roman Pontiff can, and ought to, reconcile himself, and
come to terms with progress, liberalism and modern civilization.’In thefirst
year of his pontificate Leo issued the encyclicalAeterni Patris(1879), laying out
the terms of this reconciliation. The church, he said, is adomus saptientiae,
having a twofold pedagogy of philosophy and theology.^2 The master of this
twofold pedagogy is St Thomas, who‘pushed his philosophic inquiry into the
reasons and principles of things’, but more importantly developed analogies
between‘things naturally known’and the theological‘mysteries’.^3
Just as urgently, Leo had to harmonize the conciliar documentPastor
aeternus(1870), which solemnly declared the universal jurisdiction of the
Holy See, with the life of social and political institutions that were no longer
constituted in juridical Christendom. Vatican I declared the death ofde facto
national churches—a one-way separation, so to speak, of the church from
temporal powers. Political Christendom as it had existed in Latin Christianity
for some 1,600 years was over; to the astonishment of European cabinets and
public opinion, this was done by the hand of the church, not the state. But no
one had a playbook for how an autonomous church on paper could success-
fully interface on the ground with modern institutions—institutions which
were, at best wary, if not openly hostile to the liberty of the church. It fell to
Leo tofigure out a game plan.^4 He went on the offensive, writing some 110
encyclicals in which he attempted to distinguish and harmonize diverse social
forms, modes of authority, and institutions:Diuturnum(1881),Immortale Dei
(1885),Libertas praestantissimum(1888). Once again, he recommended the
teachings of St Thomas for the‘true meaning of liberty’and for the‘divine
origin of all authority’.^5
Whereas Vatican I produced only two documents, the Second Vatican
Council produced sixteen. The intellectual, doctrinal, and even the pastoral
threads connecting these documents were rather loosely woven. Over nine
sessions (1962–5), the council issued both a dogmatic and a pastoral constitution
(^2) On the situation of nineteenth-century Thomism and the Leonine revival, see my essay:
‘Two Modernisms, Two Thomisms: Reflections on the Centenary of Pius X’s Letter against the
Modernists’,Nova et Vetera5/4 (Fall 2007), 843–79.
(^3) Aeterni Patris§18.
(^4) For Leo’s contribution to both the faith–reason and church–state issue of the era, see my
work:The Teachings of Modern Christianity: On Law, Politics, and Human Nature, 2 vols, ed.
John Witte and Frank Alexander (New York: Columbia University Press, 2005). In vol. 1, see
‘Introduction to Catholic Authors’, and‘Pope Leo XIII’,3–38, 39–74.
(^5) Aeterni Patris§29.
Christian Humanism and the Crisis of Modern Times 241