Pope Pius XI
Who died 70 years ago yesterday. From Rorate Cæli.

No reason, however grave, may be put forward by which anything intrinsically against nature may become conformable to nature and morally good.

The union of Christians can only be promoted by promoting the return to the one true Church of Christ.

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.

It is clear why Modernists are so amply justified in fearing no Doctor of the Church so much as Thomas Aquinas.

Whoever exalts race, or the people, or the State, or a particular form of State, or the depositories of power, or any other fundamental value of the human community — however necessary and honorable be their function in worldly things — whoever raises these notions above their standard value and divinizes them to an idolatrous level, distorts and perverts an order of the world planned and created by God; he is far from the true faith in God and from the concept of life which that faith upholds.

The Church, being a society of men, cannot exist or develop if it does not enjoy liberty of action, and that its members have the right to find in civil society the possibility of living according to the dictates of their consciences.

Communism is intrinsically wrong, and no one who would save Christian civilization may collaborate with it in any undertaking whatsoever.

It would be a grave error, on the other hand, to say that Christ has no authority whatever in civil affairs...

Of course one may have different opinions on exactly how that plays out there. I belong to the secular (not secularist) right.