Pope Leo XIII declared in his 1885 encyclical Immortale Dei
that the church was not committed to any particular form of government and that she could work with all, but he also went on to condemn freedom of religion and freedom of the press as threats to civil society and true religion.
Among the most important encyclicals are: Inscrutabili Dei Consilio, "On the Evils of Society," 1878; Quod Apostolici Muneris, "On the Evils of Socialism," 1878; Aeterni Patris, "On the Restoration of Christian Philosophy," 1879; Arcanum, "On Christian Marriage," 1880; Diuturnum, "On the Origin of Civil Power," 1881; Immortale Dei
, "On the Christian Constitution of the State,"1885; Libertas, "On the Nature of Human Liberty," 1888; Exeunte lam Anno, "On the Right Ordering of Christian Life," 1888; Sapientiae Christianae, "On Christians as Citizens," 1890; Rerum Novarum, "On Capital and Labor," 1891; Graves De Communi Re, "On Christian Democracy," 1901.
Similarly, the fourteen pages devoted to the doctrine of subsidiarity note its origin in late nineteenth and early twentieth century papal encyclicals, especially Immortale Dei
(1885) and Quadragesimo Anno (1931).
While La Piana traces the participation of Catholics in the political realm from the early days of the Republic, he points to a particularly notable papal blessing of sorts for the participation of Catholics in politics with the words of Pope Leo XIII in Immortale Dei
(1885): "It is evident that Catholics have just reasons to get into politics; but they must do this, not because they can approve of what is deplorable in the present political institutions of their country, but in order to use those institutions in such a way as to secure the public good, and with the purpose of injecting in all the veins of the State, as a new vital blood, the virtue and influence of the Catholic religion.