“If you want peace, work for justice,” Pope Paul VI famously said in 1972. The aphorism, part of his Message for the World Day of Peace, soon showed up on posters and bumper stickers. Though some of the faithful viewed the sentiment as a passing fad of progressive Catholics in the 1970s, the truth remains that justice is a prerequisite for peace.

In his Message for the 45th World Day of Peace, which is observed Jan. 1, Pope Benedict XVI takes up and develops Pope Paul’s theme in his own characteristic way. Benedict alludes to the economic crises that continue to wrack the world — crises that could very well lead to serious conflicts. “It seems as if a shadow has fallen over our time, preventing us from clearly seeing the light of day,” he writes. But young people, ever idealistic and hopeful, continue to believe that a “dawn” will pierce this shadow, he notes.

Apparently referring to the Occupy Wall Street movement that gained international attention in 2011, the Pope states: “The concerns expressed in recent times by many young people around the world demonstrate that they desire to look to the future with solid hope. At the present time, they are experiencing apprehension about many things: They want to receive an education that prepares them more fully to deal with the real world; they see how difficult it is to form a family and to find stable employment; they wonder if they can really contribute to political, cultural and economic life in order to build a society with a more human and fraternal face.”

For that reason, the Pope states, the proper education of youth is of utmost importance, and he makes his theme for the message “Educating Young People in Justice and Peace.”

It is a task to which many are called: Parents should “encourage children by the example of their lives to put their hope before all else in God, the one source of authentic justice and peace.” Those in charge of educational institutions need to “reassure families that their children can receive an education that does not conflict with their consciences and their religious principles.”

And what is the first lesson? “Learning to recognize the Creator’s image in man, and consequently learning to have a profound respect for every human being and helping others to live a life consonant with this supreme dignity,” says the Pope.

That is the reason for acting justly.

In an increasingly secular world, many will ignore such counsel. But even those who do not acknowledge God are called to recognize the natural law, which calls us to live justly and, therefore, in peace. This begins with a recognition of an objective truth about humanity and about the universe.

“In order to exercise his freedom,” Pope Benedict declares, “man must move beyond the relativistic horizon and come to know the truth about himself and the truth about good and evil. Deep within his conscience, man discovers a law that he did not lay upon himself, but which he must obey. Its voice calls him to love and to do what is good, to avoid evil and to take responsibility for the good he does and the evil he commits.

“If you want peace, work for justice,” indeed. But justice is done only when we recognize that universal code, written in the heart of man, that is intimately tied to the dignity of every person.