Murray on Leo XIII and church-state separation, correctly understood

And while we are on the subject of Pope Leo XIII, Evangelical Catholicism, and church-state relations, well understood, it is well worth reading John Courtney Murray's paper, "Leo XIII:  Separation of Church and State":

Leo XIII developed the theory and practice of Church-State relationships amid the conditions created by the peculiar nineteenth-century plight of the so-called Catholic nations of Europe and Latin America. The major feature of the situation consisted in the efforts of an activist ideological sect to effect, through the control and use of governmental power, the politico-social change known as "separation of Church and state." This current phrase was pregnant both of an ideology and of a political and social program. It meant, first, the alteration of the Christian structure of politics, which had been characterized by the traditional duality of Church and state, in the direction of a juridical and social monism. It meant, secondly, the evacuation of the Christian substance of society through the establishment of a surrogate political religion which went by the name of "laicism." The first subject of the present article is separation of Church and state in this pregnant sense, which is the sense in which Leo XIII understood the thing. . . .