Rerum novarum (from its incipit, with the direct translation of the Latin meaning "of revolutionary change"[n 1]), or Rights and Duties of Capital and Labor, is an encyclical issued by Pope Leo XIII on 15 May 1891.

[7][8] "Zigliara also helped prepare the great encyclicals Aeterni Patris and Rerum novarum and strongly opposed traditionalism and ontologism in favor of the moderate realism of Aquinas.

In this document, Pope Leo XIII articulates the Catholic Church's response to the social conflict in the wake of capitalism and industrialization which had provoked socialist and communist movements and ideologies.

If through necessity or fear of a worse evil the workman accept harder conditions because an employer or contractor will afford him no better, he is made the victim of force and injustice.

Although the encyclical follows traditional teaching concerning the rights and duties of property and the relations of employer and employee, it applies the old doctrines specifically to modern conditions (hence the title).

[13] Pope Leo XIII saw certain expressions of socialism as fundamentally flawed, seeking to replace rights and Catholic moral teaching with the ideology of state power.

They hold that by thus transferring property from private individuals to the community, the present mischievous state of things will be set to rights, inasmuch as each citizen will then get his fair share of whatever there is to enjoy.

They are, moreover, emphatically unjust, for they would rob the lawful possessor, distort the functions of the State, and create utter confusion in the community[15]To build social harmony, the Pope proposes a framework of reciprocal rights and duties between workers and employers.

Leo states that "...according to natural reason and Christian philosophy, working for gain is creditable, not shameful, to a man, since it enables him to earn an honorable livelihood.

The Catechism of the Catholic Church lists three principal aspects of the common good: 1) respect for the human person and his rights; 2) social well-being and development; and 3) peace, "the stability and security of a just order.

"[21] Pope Leo strongly criticizes socialism for seeking to replace the rights and duties of parents, families and communities with the central supervision of the state.

By the same token, if there occur a grave disturbance of mutual rights within a household, public authority should intervene to give each party its proper due.

[23]God Himself seems to incline rather to those who suffer misfortune; for Jesus Christ calls the poor "blessed"; (Matt.5:3) He lovingly invites those in labor and grief to come to Him for solace; (Matt.

Now, there is a good deal of evidence in favor of the opinion that many of these societies are in the hands of secret leaders, and are managed on principles ill-according with Christianity and the public well-being; and that they do their utmost to get within their grasp the whole field of labor, and force working men either to join them or to starve.

"[11] In 2016, the left-wing periodical Jacobin judged that, from a socialist perspective, Rerum novarum was "uncomfortably" situated between laborers and industrialists, and that "it both opened up space for anticapitalist critique and severely restricted its horizons..."[34] With the regime established in Portugal under António de Oliveira Salazar in the 1930s, many key ideas from the encyclical were incorporated into Portuguese law.

According to historian Howard J. Wiarda, its basic policies were deeply rooted in European Catholic social thought, especially those deriving from Rerum Novarum.

Wiarda concludes that the Catholic social movement was not only powerful in its own right but it also resonated with an older Portuguese political culture which emphasized a natural law tradition, patrimonialism, centralized direction and control, and the 'natural' orders and hierarchies of society.