It is no coincidence that in the same years at the end of the 19th century two perfectly compatible phenomena incubated, such as Catholic modernism and Marxism/socialism/communism. Karl Marx's Communist Manifesto dates to 1848 and the process that led to communist regimes continued over the following decades.
The Magisterium has taught us that communism and Catholicism are incompatible, yet how many Catholics have contributed to the obvious shift to the left of Catholic culture that has been so evident in recent years? We are well aware of the “Christians for Socialism” and other similar movements that have attempted a synthesis that, despite the good intentions of some, has always failed.
Pius IX in his 1846 Encyclical Qui Pluribus (two years before the Communist Manifesto!) already clearly warned: "This is the aim of the nefarious doctrine of Communism, as they say, most adverse to natural law itself: once it is accepted, the rights of all, things, property, indeed human society …More