If Socialism, like all errors, contains some truth (which, moreover, the Supreme Pontiffs have never denied), it is based nevertheless on a theory of human society peculiar to itself and irreconcilable with true Christianity. Religious socialism, Christian socialism, are contradictory terms; no one can be at the same time a good Catholic and a true socialist.
Pope Pius XIMen will see in their king or in their rulers men like themselves perhaps unworthy or open to criticism, but they will not on that account refuse obedience if they see reflected in them the authority of Christ, God and Man. Peace and harmony, too, will result; for with the spread and the universal extension of the kingdom of Christ, men will become more and more conscious of the link that binds them together, and thus many conflicts will either be prevented entirely or at least their bitterness be diminished.
Pope Pius XIEducation belongs pre-eminently to the church ... neutral or lay schools from which religion is excluded are contrary to the fundamental principles of education.
Pope Pius XIWhen once men recognize, both in private and in public life, that Christ is King, society will at last receive the great blessings of real liberty, well-ordered discipline, peace and harmony.
Pope Pius XIIt is not enough to be a member of the Church of Christ, one needs to be a living member, in spirit and in truth, i.e., living in the state of grace and in the presence of God, either in innocence or in sincere repentance.
Pope Pius XIFor they have always unanimously maintained that nature, rather the Creator Himself, has given man the right of private ownership not only that individuals may be able to provide for themselves and their families but also that the goods which the Creator destined for the entire family of mankind may through this institution truly serve this purpose.
Pope Pius XI