Quadragesimo anno marks the fortieth anniversary of Pope Leo XIII’s Rerum novarum, which it briefly reviews and then expands upon. Whereas Leo focuses more narrowly in Rerum novarum on the spiritual and economic oppression of workers in conjunction with his defense of labor unions and other private societies, Pope Pius XI expands his scope to comment on the twin perils of individualism and collectivism, propose a more active role for the state in relation to the economy, and articulate the need for the harmonious interrelation of different classes, industries, and professions—what has come to be known as corporatism in Catholic social thought. Pius rearticulates Leo’s critique of socialism—famously, he concludes an extended discussion of socialism, which he takes pains to differentiate from communism as practiced in the Soviet Union, with the claim that “religious socialism, Christian socialism, are contradictory terms; no one can be at the same time a good Catholic and a true socialist” (120). At the same time, he offers a more robust critique than Leo of free-market capitalism and stresses workers’ right to a just wage. All in all, Pius is sensitive to socialism’s critique of capitalism; he concedes that “socialism inclines toward and in a certain measure approaches the truths which Christian tradition has always held sacred” (113). His rejection of socialism is less reactionary than Leo’s and primarily focuses on its indifference toward humans’ supernatural end.
Perhaps most importantly, Quadragesimo anno explicitly articulates the principle of subsidiarity, a central element of Catholic social thought only hinted at in Rerum novarum. Pius formulates the principle as follows: “Just as it is gravely wrong to take from individuals what they can accomplish by their own initiative and industry and give it to the community, so also it is an injustice and at the same time a grave evil and disturbance of right order to assign to a greater and higher association what lesser and subordinate organizations can do” (79). Put differently, the principle of subsidiarity states that the ends and rules proper to each subsidiary community or association constitutive of civil society should be respected, and that social and political conflicts should be addressed at the level that is most conducive to their resolution. For Pius, this principle is especially important in view of “individualist” political philosophies that posit only the existence of individual citizens, on the one hand, and the state, on the other, with no mediatory communities or associations. The principle both keeps in check state power and liberates the state to execute those functions that it alone is equipped to perform. While the principle of subsidiarity has its roots in the philosophy of Thomas Aquinas, it was not until Quadragesimo anno that the principle came to occupy a central place in Catholic social thought. Subsequent iterations on the principle take Pius’s formulation as their point of departure.