33 There is another and deeper consideration which must not be lost sight of. As regards the State, the interests of all, whether high or low, are equal. The members of the working classes are citizens by nature and by the same right as the rich; they are real parts, living the life which makes up, through the family, the body of the commonwealth; and it need hardly be said that they are in every city very largely in the majority. It would be irrational to neglect one portion of the citizens and favor another, and therefore the public administration must duly and solicitously provide for the welfare and the comfort of the working classes; otherwise, that law of justice will be violated which ordains that each man shall have his due. To cite the wise words of St. Thomas Aquinas: "As the part and the whole are in a certain sense identical, so that which belongs to the whole in a sense belongs to the part."(27) Among the many and grave duties of rulers who would do their best for the people, the first and chief is to act with strict justice - with that justice which is called distributive - toward each and every class alike.
Source: Rerum Novarum (Vatican.va)