An encyclical issued by Paul VI on March 26, 1967 concerning the development of peoples, reflecting on the progress of society:

"...certain concepts have somehow arisen out of these new conditions and insinuated themselves into the fabric of human society. These concepts present profit as the chief spur to economic progress, free competition as the guiding norm of economics, and private ownership of the means of production as an absolute right, having no limits nor concomitant social obligations.

This unbridled liberalism paves the way for a particular type of tyranny, rightly condemned by Our predecessor Pius XI, for it results in the "international imperialism of money."

Such improper manipulations of economic forces can never be condemned enough; let it be said once again that economics is supposed to be in the service of man."

Phillip Berryman wrote:
Within its generally moderate tone the encyclical hinted at a strong critique of the existing international economic order. The Wall Street Journal called it "warmed-over Marxism." ...In Latin America the most quoted passage was paragraph 31:

We know.. that a revolutionary uprising - save where there is manifest long-standing tyranny which would do great damage to fundamental personal rights and dangerous harm to the common good of the country - produces new injustices, throws more elements out of balance and brings on new disasters.
Shortly afterward, a group of eighteen Third World bishops, half from Brazil, drew up a statement that went considerably further than the pope's, while quoting him abundantly. They took a positive view of revolution and approvingly quoted the statement of a bishop during Vatican II: "Authentic socialism is Christianity lived to the full, in basic equality and with a fair distribution of goods."

Full text: http://www.vatican.va/holy_father/paul_vi/encyclicals/documents/hf_p-vi_enc_26031967_populorum_en.html