Christians contend that theology can be harmonized with science. Both disciplines pursue the same object—truth—and by that common object are unified. Even methodologically, science and religion are complementary. As Pope St. John Paul II duly observed, “Science can purify religion from error and superstition; religion can purify science from idolatry and false absolutes.” Among the many scientists who would agree with John Paul II, one of the greatest modern advocates for the complementarity of science and religion has been Sir John Polkinghorne, the distinguished particle physicist and Anglican priest.

Polkinghorne, who recently died at the age of ninety, obtained a doctorate in quantum field theory from Cambridge in 1956. He obtained a second doctorate in elementary particle physics in 1974. A few years later he left his research post (to the shock of many) to pursue theological studies, eventually being ordained as a priest in the Church of England in 1982. Polkinghorne became a key proponent for the reciprocal complementarity of theology and science (writing almost thirty books on the topic), and of the unique ability of the Christian worldview to broaden and deepen one’s vision of reality in both its physical and metaphysical domains.

Evolutionary biologist Stephen Jay Gould famously contended that science and religion constitute “non-overlapping magisteria.” He proposed the idea of a hard separation between the domains of science and religion. As a result of this separation, the domains may in no way be said to be in conflict with—or to complement—one another. His theory had the favorable effect, perhaps, of maintaining the fact that scientific thinking is not in conflict with Christian doctrine. But, ultimately, the theory is too radical. It goes too far.

It seems obvious that science and religion do overlap to some degree. The origin of the cosmos, for instance, is something that both scientists and theologians muse about in common, but from different vantage points. This reinforces the fact that there is more than one way to think about what we experience with the senses. Astrophysics and philosophy, for instance, instantiate distinct modes of inquiry. But they share a common subject. They need not be blindly taken as competitive with one another.

“Some religions make claims about matters on which science has something to say,” writes particle physicist Stephen Barr. “And some scientific discoveries are relevant to important philosophical questions. So, theology cannot be walled off from science.” Certainly, the astrophysicist and the metaphysician can have some very interesting conversations about, say, the origin of our universe, speaking from the perspectives of their own specializations, and offering each other new perspectives that they could not have gleaned if they were to stick strictly to their own area of inquiry.

And we can say more about the inherent coherence of theological thinking with that of science. For every time we advance in the scientific method to the “analysis” step, we consider the data we have collected logically and infer new conclusions, next steps, and ethical considerations. Science is an intrinsically inductive practice, drawing probable general conclusions from particular data. Science is probabilistic because it is essentially inductive. And to say that something is inductive in nature is to say that the same thing is philosophical in nature. Though science is not philosophy per se, it is to an extent philosophical.

John Polkinghorne understood this, and had a great gift for incorporating science, philosophy, and theology in his writings. Though deep and insightful, he was also clear and accessible. Moreover, his familiarity with the smallest aspects of reality allowed him a unique and intriguing perspective. Some Christian apologists, following in the footsteps of William Paley, have shown an affinity for comparing the universe to a clock. They have argued that the clock-like structure (and the intelligibility it grants) reflects a divine designer—a divine “clockmaker.”

Polkinghorne didn’t denigrate the clock analogy, but he thought that a cloud was more fitting.

We all have a standard view of the world as we experience it, what Wilfrid Sellers called the “manifest image” of reality. It is undeniable that the universe takes on an obviously mechanistic appearance at our basic level of experience. The fittingness of Polkinghorne’s cloud analogy, on the other hand, makes best sense from a bottom-up perspective. At the quantum level, it is well known that things get remarkably weird or “spooky” (as some quantum theorists have put it). This fuzziness of the quantum realm interlocks with the concreteness of the “manifest image” of common experience; somehow, the cloud merges with the clock, forming one composite reality.

It is not only the physical world that’s of such a hierarchical nature. The structure of reality itself consists of hierarchy, and each level appropriates itself to the others—and to our minds—in unique ways. This theme is explored in depth by Jacques Maritain in his magisterial book The Degrees of Knowledge. He observes, for instance, that mathematics—the most fundamental aspect of the observational sciences—necessarily elicits in us an “appetite” for the metaphysical. In the immaterial realm of the mind, mathematical abstraction naturally provokes one to go another “level” deeper into metaphysical abstraction.

If Maritain is right about mathematics naturally giving way to metaphysics, it is no surprise that someone like Polkinghorne was so drawn through science to the religious. Reciprocally, it can be assumed that as he matured in his religious convictions, they instilled in him an increasingly robust scientific attitude. This propensity to move from religion to science is reflected by a line written by Polkinghorne’s fellow countryman C.S. Lewis in his book Miracles: “Men became scientific because they expected law in nature, and they expected law in nature because they believed in a lawgiver.”

Like Maritain, Polkinghorne adopted a view of the world he called critical realism. Though their unique uses of the term may surely be differentiated, both were profoundly influenced by the realist philosophy of St. Thomas Aquinas. Like Aquinas, both Maritain and Polkinghorne believed that the sensible things perceived outside ourselves are really there. In terms of scientific knowledge about the world, Polkinghorne insisted on “the positive relationship of scientific knowledge to the way the world is.”

Though skepticism abounded in the culture that surrounded him, Polkinghorne thought real epistemic certainty was entirely possible about religious matters and about matters concerning the world in general. He also recognized that certainty can be reflexively critical. That is, we can think critically even about our own certainties. While we can be rationally certain about our scientific conclusions, for instance, our convictions, or near-convictions, are always founded on assumptions, scientific (e.g., other scientists’ conclusions) and non-scientific (e.g., the validity of inference). There is always room for honest criticism of our thinking, but that fact in no way diminishes the possibility of a meaningful degree of certainty. We can possess knowledge with varying degrees of certainty—but with certainty, nonetheless. We find in Polkinghorne’s critical realism, thus, a fine balance of humility and optimism.

Faith involves the assent of intellect and will to that which cannot, either by circumstance or in principle, be directly proven. Quantum physicists assume an attitude similar to the posture of faith. At the deepest level of known physical reality, complete descriptions are unobtainable. Our best descriptions are always incomplete and must be inferred or calculated indirectly from what we do know. This is how the existence of certain fundamental particles is determined. “The existence of quarks,” writes Polkinghorne in Science and Religion in Quest of Truth, “must be defended by appeal to the intelligibility that they offer to more directly accessible phenomena.” Just as quantum physicists derive knowledge about the unobservable from the observable, so also do philosophers and theologians do the same when it comes to inferring knowledge about God from what is accessible to the senses. This analogous relationship between scientific and religious modes of knowledge suggests why Polkinghorne was so adroit in talking about both dimensions of reality, and in relating them sympathetically with such ease and proficiency.

Sir John Polkinghorne was convinced that, ultimately, science, philosophy, and theology are all directed toward one and the same thing: truth. Since all facts of reality—physical and metaphysical—are grounded in one necessary and divine source, the eternal Logos, truth itself is one. The Grand Unified Theory sought by his scientific colleagues was, Polkinghorne knew, a person.

We will miss the depth of vision, clarity, and creativity of John Polkinghorne. Though he has gone on to his eternal reward, he has left us with much to be thankful for. I suspect we will be reading his books and discussing his ideas for quite some time.