In the encyclical Pacem in terris (April 11, 1963), John XXIII says:
“It is impossible to determine in all cases what is the most suitable form of government, or how civil authorities can most effectively fulfill their respective functions, i.e. legislative, judicial, and executive functions of the State.
“In determining the structure and operation of government which a State is to have, great weight has to be given to the circumstances which will vary at different times and in different places.”
Plinio Corrêa de Oliveira, Nobility and Analogous Traditional Elites in the Allocutions of Pius XII: A Theme Illuminating American Social History (York, Penn.: The American Society for the Defense of Tradition, Family, and Property, 1993), Appendix IV, p. 395.