Pius XI (1922-1939)
Mortalium Animos, January 6, 1928
"on religious unity"
So, Venerable Brethren, it is clear why this Apostolic See has never allowed its subjects to take part in the assemblies of non-Catholics: for the union of Christians can only be promoted by promoting the return to the one true Church of Christ of those who are separated from it, for in the past they have unhappily left it.  To the one true Church of Christ, we say, which is visible to all, and which is to remain, according to the will of its Author, exactly the same as He instituted it [#10].


Roman Question
Rappresentanti in Terra, Dec 31, 1929
"on Christian education"
False also and harmful to Christian education is the so-called method of “co-education.” . . . there is not in nature itself, which fashions the two [sexes] quite different in organism, in temperament, in abilities, anything to suggest that there can be or ought to be promiscuity [indiscriminate mixing or mingling], and much less equality in the training of the two sexes.  These, in keeping with the wonderful designs of the Creator, are destined to complement each other in the family and in society, precisely because of their differences, which therefore ought to be maintained and encouraged during their years of formation, with the necessary distinction and corresponding separation, according to age and circumstances,  These principles, with due regard to time and place, must, in accordance with Christian prudence, be applied to all schools, particularly in . . . adolescence . . . (# 68).

Casti Connubii December 30, 1930
"on Christian marriage"

Quadragesimo Anno, May 15, 1931
Dorothy Day (Catholic Worker)
"All are called to be saints, not to do the extraordinary--if sanctity depended on doing the extraordinary, there would be few saints."


Concordat with Third Reich


Mit Brennender Sorge, March 14, 1937
Divini Redemptoris, March 19, 1937