What are the odds that on one Sunday I would come across the same exact phrase used by two men more than half a century apart?

One man was Nobel Prize-winning physicist Niels Bohr; the other was Pope St. John Paul II. This is the phrase: “Different human cultures are complementary.”

I first found it in Fides et Ratio (The Relationship Between Faith and Reason) while preparing a lecture for a Catholic theology of science course I teach at Seton Hall University. The class was studying the religions of ancient cultures and their contributions to modern science, and the unifying phrase fit the lesson.

Later that day, I heard the same phrase again while listening to the narration of The Making of the Atomic Bomb by Richard Rhodes. He used it in a very different context, but I think there is a connection.

Niels Bohr is, of course, the Danish physicist who received the Nobel Prize in Physics in 1922 for furthering the knowledge of atomic structure through quantum theory. “Complementarity” was his trademark word. He used it to describe the particle-wave duality of light in what later became known as the “Copenhagen interpretation.” It derives from the Latin complementum (“that which fills up or completes”).

Since light can be described as both a particle and a wave, Bohr thought these depictions represent mutually exclusive abstractions that complete each other, both equally valid, together forming a composite picture of the atom.

Bohr was also a philosopher and an atheist, and he stretched this word outside of physics often. Like many of his colleagues in the late 1930s, Bohr was troubled that the new knowledge of the fundamental nature of matter was being used to construct the atomic bomb, the very weapon that could eradicate humanity.

He saw the bomb as paradoxical. If statesmen could be made to understand the danger of a nuclear holocaust, he thought, then they might unite to ban nuclear weapons. Bohr coined the phrase “complementarity of the bomb” to illustrate its function as both an annihilator and savior of mankind.

The racism of Nazi Germany greatly disturbed Bohr, too. In the summer of 1938, he was invited to give an address in a castle at the International Congress of Anthropological and Ethnological Sciences in Helsingor, Denmark, on the coast of Zealand north of Copenhagen. Bohr’s fame had earned him substantial influence by then, and he used the occasion to challenge Nazi racism publicly. He used his trademark word to describe the dangers of prejudice. Here is the phrase, cited by Rhodes in The Making of the Atomic Bomb, but in its original context:

“Using the word much as it is used, in atomic physics, to characterize the relationship between experiences obtained by different experimental arrangements and visualizable only by mutually exclusive ideas, we may truly say that different human cultures are complementary to each other. Indeed, each such culture represents a harmonious balance of traditional conventions by means of which latent potentialities of human life can unfold themselves in a way which reveals to us new aspects of its unlimited richness and variety” (Bohr, Atomic Physics and Human Knowledge, 30).

According to Rhodes, the German delegates walked out of Bohr’s speech. He’d hit his mark.

One cannot help but admire Bohr’s resolve to defend humanity. Yet his logic was not quite complete. It was human-centered, focusing down from science, viewing all in the framework of science. It was scientism.

Bohr began that speech by saying that “it is impossible to distinguish sharply between natural philosophy and human culture” because science has clarified the background of our existence. Bohr thought science would set man free (Rhodes, 243).

In a sense, Bohr was right to objectify the human condition so that rationality might prevail, but his point never made it much beyond that conference, for good reason. To call human cultures complementary only begs questions. The phrase, on its own, is fraught with platitude.

What, exactly, does it mean for an atheist to say humanity is united in a harmonious balance of traditional conventions? That there are “latent potentialities of human life” with “unlimited richness and variety”? Was he talking about happiness?

Salvation perhaps?

Bohr said in that speech that the common aim of all science was to “gradually remove prejudices.” But he struggled with his epistemology and tried to soften the blow. He explained that the use of the word “prejudice” meant pre-judgment of a logical framework, true to his physicist rigor, and he withheld contempt for those cultures who judged other cultures worthy of extinction. He concluded with an acknowledgment that he had “talked in a very obscure way,” as if he knew he left a great deal unsaid, which brings us to Pope John Paul II.

Popes pick words carefully in encyclicals, and I contend that those five words — “Different human cultures are complementary” — are too specific and unique for the repetition to have been happenstance. The two men’s paths must have crossed, at least intellectually. I’ll sketch the air of the time.

In the year Bohr gave the speech in a castle with anthropologists in Zealand, the future pope, Karol Wojtyła, was 18 years old and had begun philosophy studies at the Jagiellonian University in Kraków. By 1939, Nazi German forces closed Wojtyła’s university, and he was forced to do manual labor to avoid deportation to Germany. Wojtyła worked in a limestone quarry, which left him with permanent injuries. Then he found work at the Solvay chemical factory.

Ernest Solvay was the Belgian chemist who developed the ammonia-soda process for making sodium hydrogen carbonate (baking powder) used in the production of soap, textiles and glass. Solvay is also the philanthropist who used his wealth to, among other things, begin a series of conferences in chemistry and physics, known as the Solvay Conferences. These conferences, from 1911 to 1933, played a key role in bringing quantum theory to the forefront of physics, hosting such leading figures as Bohr, Albert Einstein, Marie Curie, Erwin Schrödinger, Wolfgang Pauli, Werner Heisenberg, Paul Dirac, Arthur Compton, Louis de Broglie, Max Born, Max Planck and Hendrik Lorentz.

After the Second World War, Wojtyła continued his studies in Kraków at a clandestine seminary and then at Jagiellonian once more when it reopened. He was ordained to the priesthood in 1946. Hence, Wojtyła was educated in the climate in which the discovery of atomic structure took place, and the cultural dangers Bohr spoke of were real for the young Wojtyła.

By 1998, when Fides et Ratio was promulgated, Bohr’s prognostication about the complementarity of the bomb had not played out either. The bomb was neither the destroyer nor the savior of mankind. Today, technology unites us globally more than ever, but the entire population of planet Earth remains at a nuclear standoff. Weapons have not brought world peace.

This provides a backdrop for Fides et Ratio. The Pope says that humans have always searched for truth, to know reality and know ourselves. The admonition “Know Yourself” is not of Christian origin, though. It is carved on the ancient Greek temple portal at Delphi. The encyclical names different human cultures and acknowledges how they have been united in a search for truth.

The sacred writings of Israel have similarities to those in the ancient Indian Veda, the ancient Iranian (Zoroastrianism) Avesta, the ancient Chinese writings of Confucius and Lao-Tze, and the preaching of Tirthankara and Buddha, the poetry of Homer, the tragedies of Euripides and Sophocles, and the philosophy of Plato and Aristotle.

Then the encyclical says that the Church is no stranger to the journey of discovery, and the Paschal Mystery is the gift of the ultimate truth about human life. Jesus Christ is “the Way, and the Truth, and the Life” (John 14:6). The Church is a pilgrim serving humanity by proclaiming the fullness of truth. Pope John Paul II emphasizes the importance of philosophy to probe life’s meaning. According to Greek etymology, philosophy means “love of wisdom.”

Here, he echoes Bohr:

“It is an innate property of human reason to ask why things are as they are, even though the answers which gradually emerge are set within a horizon which reveals how the different human cultures are complementary” (3).

Notice the difference in how the phrase is used. Where the physicist used science to describe human nature, the Holy Father says it is human nature to do science.

Interestingly, in the paragraph following the phrase in Fides et Ratio, Pope John Paul II addresses the temptation of “philosophical pride” (4). To identify a single trendy stream of thought, such as complementarity, with the whole of philosophy gives an incomplete reading of reality. Every philosophical system, even physics and especially anthropology, must be “respected in its wholeness.”

The Pope goes on to discuss how the scientific revolution caused a divide between faith and reason. For the ancients, he says, the study of the natural world and philosophy coincided (19). He cites the Book of Wisdom, that the intelligence of humans means we can “know the structure of the world and the activity of the elements ... the cycles of the year and the constellations of the stars, the natures of animals and the tempers of wild beasts” (Wisdom 7:17, 19-20).

The book of nature is read with human reason and is a first stage of divine Revelation. Thus science can lead to knowledge of the Creator. If humans do not recognize God as Creator, it is not because we lack the means to do so, but because free will and sinfulness block the way.

The encyclical describes the organic link between theology and philosophy, including natural philosophy, in the first universities from the late Middle Ages (45). But the two forms of learning suffered a separation. The separation led to a positivistic mentality that was at odds with the Christian worldview. The overemphasis on rationalism (reason without faith) led to the crisis of nihilism, the philosophy of nothingness, in which the search is an end unto itself without any hope of attaining the truth. Hence, Pope John Paul II directly addressed the scientism that so influenced the scientists of Bohr’s time (88).

Scientism is the philosophical notion that refuses to admit other forms of knowledge besides those from the positive sciences. In this view, science dominates all aspects of human life, but in doing so, it consigns the meaning of life to the realm of the imaginary, just as Bohr had indeed done in his 1938 speech.

The end of the encyclical addresses scientists specifically (106). In the 20th century, scientific achievements brought knowledge of the universe, the details of animate and inanimate components and complex atomic and molecular structure, all interacting as a whole.

Wholeness is not only key to doing science, but key to Catholicism. The Pope urged scientists to continue their efforts without abandoning the sapiential horizon, the wisdom that sets homo sapiens apart. Scientists, he says, understand that the search for truth points beyond to something higher.

So there it is: Where Niels Bohr spoke emphatically about the earthly dangers of the bomb, Pope John Paul II spoke of the eternal dangers of nihilism. Where Bohr tried to articulate human interaction and the longing for peace using the language of quantum theory, and stumbled into ambiguity, John Paul II soared to the ultimate unity of truth on the wings of faith and reason.

It seems that with the appropriation of these five specific words — “different human cultures are complementary” — the Pope reached a hand across time and space to lift the physicist’s ideas out of scientism and into the fuller truth about the human person made in the image and likeness of God. He perfected Bohr’s thought, made it complete, and supplied what is wanting. It seems the Pope turned the word around and complemented the physicist.

Stacy A. Trasancos, Ph.D.,

is the author of 

Particles of Faith: A Catholic Guide to Navigating

Science (Ave Maria Press).