19 The great mistake made in regard to the matter now under consideration is to take up with the notion that class is naturally hostile to class, and that the wealthy and the working men are intended by nature to live in mutual conflict. So irrational and so false is this view that the direct contrary is the truth. Just as the symmetry of the human frame is the result of the suitable arrangement of the different parts of the body, so in a State is it ordained by nature that these two classes should dwell in harmony and agreement, so as to maintain the balance of the body politic. Each needs the other: capital cannot do without labor, nor labor without capital. Mutual agreement results in the beauty of good order, while perpetual conflict necessarily produces confusion and savage barbarity. Now, in preventing such strife as this, and in uprooting it, the efficacy of Christian institutions is marvellous and manifold. First of all, there is no intermediary more powerful than religion (whereof the Church is the interpreter and guardian) in drawing the rich and the working class together, by reminding each of its duties to the other, and especially of the obligations of justice.
Source: Rerum Novarum (Vatican.va)