Liberation Theology

In response to Richard, I think the concerns about doctrine, while important, largely misunderstand the significance of liberation theology, which can only be understood in light of the historical relationship between the Church and longstanding structures of injustice in Latin American society. 

I think it's impossible to know anything about how the Church has historically buttressed the ruling classes in  these highly unequal, racially stratified and unjust societies and deny that a theology emphasizing the need for the Church to work on behalf of the legitimate demands of those at the bottom for fundamental social change, and the relevance of those demands for how we understand the Gospel message (and vice versa), constituted something genuinely new and valuable.  And this quite radical shift in the perceived role of the Church in some of these societies flowed directly from the novel, bottom-up methodology of liberation theology I described.  That this change in the method of producing theology would yield substantial changes in content is not all that surprising.  The Church has a limited amount of political capital, and I think a theology done by someone living and working among the poor in, say, the slums of Lima, Peru,  will provide some different answers about how to spend that capital than one formulated by a well-fed, well-housed cardinal at the Vatican or by Michael Novak for that matter. (It's worth noting that, in addition to questions of Marxist influence and doctrinal purity, it was this bottom-up approach that sparked a great deal of criticism from Ratzinger in the 1980s.)

I think you're right that the social message of liberation theology is not wholly original.  I think you'll find, though, that LT  concepts like the "preferential option for the poor" and "structural sin," which became common in the encyclicals of John Paul II, were largely absent (at least in such explicit form) from authoritative documents before the rise of liberation theology.  This seems to me to point towards the theology having made a genuine contribution to the development of the Church's social doctrine.  But I think the key innovation is the priority LT places on combating structures of economic injustice, particularly in the context of Latin American society.  This was surely new and remains vital.  I also think you're right that the key question is how to go about restructuring society to improve the situation of the poor, although I suspect we would differ on what the evidence suggests are the most appropriate strategies.  (FWIW, Michael Novak's laissez faire musings on this topic are, in my view, much farther outside the mainstream of Catholic social thought that almost anything Gustavo Gutierrez has written.)

On a side note, (this is not directed at Richard but at the critics to which he refers) it's funny to me how liberation theology's insistance that the Church involve itself in demanding that governments address moral issues associated with economic justice somehow represent an inapproriate politicization of the religion, while the Church's many efforts to combat communism in Poland and elsewhere or to demand that governments address moral issues associated with, say, abortion and homosexuality, are not.