The characters of "Mater et Magistra" (Mother and Teacher) are first and foremost the relations between the wealthy and the poor in a modern economy. The work is concerned with the disparate social and economic conditions these groups experience. It cites injurious working conditions as undermining the morality, faith, and health of the poor, and especially the most vulnerable including women and children. Roncalli argued that all classes should benefit from technological advancements.

Its characters also include nations and their relations with other nations, the boundaries of national sovereignty and the role of international and inter-faith dialogue. Roncalli argued that wealthy nations have an obligation to help the poorer underdeveloped nations and emphasized the sharing of improved agricultural techniques.

"Mater et Magistra" reiterates the social teachings of Leo XIII's "Rerum novarum," Pius XI's "Quadagesimo anno," and states that an economy that exploits workers is unjust regardless of how much wealth it produces, and no matter how justly and equitably such wealth is distributed. It specifically called for worker participation in the ownership of the enterprises they worked for. While supporting the private ownership of property, the encyclical called for the "universal destination" of goods to fulfill the plan of the creator that all the world's goods are first and foremost for the worthy support of all mankind.