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 XICapitalism itself is not to be condemned. And surely it is not vicious of its very nature, but it has been vitiated.
Pope Pius XIAlways moved by religious motives, the Church has condemned the various forms of Marxist Socialism; and she condemns them today, because it is her permanent right and duty to safeguard men from currents of thought and influence that jeopardize their eternal salvation.
Pope Pius XIIt is not possible for Christians to take part in anti-Semitism. We are Semites spiritually.
Pope Pius XIThe ultimate consequences of the individualist spirit in economic life are those which you yourselves, Venerable Brethren and Beloved Children, see and deplore: Free competition has destroyed itself; economic dictatorship has supplanted the free market; unbridled ambition for power has likewise succeeded greed for gain; all economic life has become tragically hard, inexorable, and cruel.
Pope Pius XI