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Church of Reality: Max Planck on Idealism and the Role of Faith in Science

"I regard consciousness as fundamental. I regard matter as derivative from consciousness."

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This post is part of a series on the philosophical and spiritual views of prominent scientists and mathematicians. Past subjects include Erwin Schrödinger, Georg Cantor, and Barbara McClintock. Future subjects will include Albert Einstein, Werner Heisenberg, and Ernst Mach.

Max Planck’s discovery of energy quanta set the stage for contemporary quantum mechanics. In addition to his Nobel prize, Wikipedia has two separate articles listing the physical theories and scientific institutions named after him.

Planck was also a practicing Lutheran. He saw science and religion as not only compatible, but mutually reinforcing. For Planck, science and religion were based on similar assumptions and pursued the same goals.

Let’s see how Planck reconciled his faith with his work, and how religious thought influenced his ideas.


Science and Religion

The Real World

Planck really wants you to accept the existence of an external, objective reality.

This might seem like a strange horse for a physicist to beat, but as we’ve seen, not all his peers agreed. Planck spends a lot of time and energy railing against the Positivist school, which only accepts direct sensory impressions as real. The Positivists relegate external reality to the status of “useful fiction”, a story we’ve made up to help us navigate.

Planck fully acknowledges the primacy of sensory data and measurements, and credits the Positivists for recognizing this. In his lecture Religion and Natural Science, he states:

[The Positivist] theory is that physical science has no other foundation than the measurements on which its structure is erected…the positivistic outlook possesses a distinctive value; for it is instrumental to a conceptual clarification of the significance of physical laws, to a separation of that which is empirically proven from that which is not, to an elimination of emotional prejudices nurtured solely by customary views, and it thus helps to clear the road for the onward drive of research.

But he sees the Positivist view as fundamentally limited, and inadequate for science:

But Positivism lacks the driving force to be a leader on this road…For its activity is essentially critical, its glance directed backwards.

He explains that a purely Positivist viewpoint has a major blind spot: it can never see past the observer, to the reality behind the measurements.

…since every measurement presupposes an observer, from the positivistic viewpoint the real substance of a law of physics can never be detached from the observer, and it loses its meaning as soon as one attempts mentally to eliminate the observer and to see something more, something real, behind him and his measurement.

This outlook cannot be challenged from the purely logical viewpoint. And yet, a closer examination must brand this version of it as inadequate and unproductive…every physical measurement can be reproduced, so that its outcome depends neither on the personality of the individual performing the experiment, nor on the place and time of the measurement, nor on any other attendant circumstance. But this simply means that the factor which is decisive for the result of the measurement lies beyond the observer

In other words, in order to make sense of the wide agreement between experimental results, we need to step beyond Positivism, and acknowledge the existence of an objective, external reality.

Religious Symbols

Planck dislikes Atheists even more than he dislikes Positivists.

In language that borders on McCarthyist panic, he accuses “the atheist movement” of using scientific progress to further an ideological agenda:

…allegedly in alliance with natural science, the movement continues to spread at an ever quickening pace its disruptive influence over all nations and classes of mankind….the victory of atheism would not only destroy the most valuable treasures of our civilization, but—what is even worse—would annihilate the very hope for a better future.

As a scientist, Planck was keenly aware of the overt conflict between scientific and religious thought (something we’ve discussed before). He addressed the issue in Religion and Natural Science:

…he who is in earnest about his faith and cannot bear to see it conflict with his scientific learning, must decide in his conscience whether in all honesty, he may still consider himself a member of a religious community whose creed incorporates a belief in miracles.

He rejects the idea that the religious scientist can cast off most magical thinking, and hold to only a few “important” miracles, saying

The faith in miracles must yield ground, step by step, before the steady and firm advance of the forces of science, and its total defeat is indubitably a mere matter of time.

But this is not a death blow for religion. Planck sees the stories, symbols, and rituals employed by religions as secondary, as indirect attempts to point to something higher. They are like works of art, attempts to inspire a particular feeling in the observer.

It’s these symbols which are easily attacked as unscientific, and which are held up by Atheists as proof of religion’s absurdity. But Planck insists that we need to understand the symbolic nature of every outward manifestation of religion. Attacking “winged angels” as unscientific makes no more sense than attacking a fantasy novel for being fictional. Both are devices for pointing to something ineffable, and not to be taken literally.

He expresses just as much frustration towards religious zealots, who do take their symbols literally:

…we must never forget that even the most sacred symbol is of human origin.

Had mankind taken this truth to heart at all times, it would have been spared an infinity of woe and suffering. For the terrible religious wars, the horrible persecutions of heretics and their attendant tragic consequences, are in the last analysis the outcome of conflicts between opposing propositions, each possessing a certain validity and each originating in the circumstances that a common abstract idea…was confused with its visible but distinct media of expression

Leaps of Faith

There is a major parallel between Planck’s rejection of Positivism and his rejection of Atheism: Positivists deny that our direct measurements draw from an unseen objective reality; Atheists deny that our direct religious experiences draw from an unseen divinity.

He agrees that neither Positivism nor Atheism can be refuted by reason or evidence. In both cases, he is only able to make a leap of faith.

The Scientific Leap of Faith

In his book Where is Science Going?, Planck describes the tension between experimental and theoretical work in physics:

…there are two theorems that form together the cardinal hinge on which the whole structure of physical science turns. These theorems are: (1) There is a real outer world which exists independently of our act of knowing, and, (2) The real outer world is not directly knowable. To a certain degree these two statements are mutually contradictory. And this fact discloses the presence of an irrational or mystic element which adheres to physical science as to every other branch of human knowledge. [Emphasis mine.]

In Planck’s view, experimental evidence is primary, and yet each measurement is a product of a particular time, place, scientist, measuring device, etc. Any particular experiment can be discarded as fallible.

Conversely, all our theories are post-hoc constructions, derived from the primary knowledge of experiment. But they are largely unassailable, precisely because they’re supported by a wide variety of measurements.

The scientific theories we infer are generated by a deeper objective order, but we can never see that order directly. In order to see the existence of an objective reality, we need to step beyond the epistemic limits of Positivism. We need to make a leap of faith.

The Religious Leap of Faith

Planck describes the tension between religious experience and divinity in similar terms:

Does that higher power which stands behind the religious symbols and lends them their essential significance, dwell solely in the human mind, and is it obliterated also in the moment when that mind ceases to exist, or does it stand for something more? In other words: Does God live in the soul of the believer only, or does He rule the world independently of whether or not one believes in Him? This is the point at which minds part company basically and decisively.

He points to the commonalities of religious experience (also something we’ve discussed before) as an analog of agreements in scientific measurements:

A common feature of all [religions] consists in the rather natural assumption of a personified or at least an anthropomorphic deity. This leaves room for the most diverse concepts of the attributes of God. Each religion has its own distinct mythology and also its own distinct rituals, elaborate to the most minute details in the more highly developed religions. These are the source of certain interpretive symbols of religious worship, which are capable of acting directly on the imagination of the great masses, arousing their interest in religious matters and giving them a certain understanding of the deity.

…On the other hand, a religious symbol always points beyond itself. Its significance is never exhausted by its own features, however much veneration it may enjoy…religious symbols [are] subject to certain inevitable changes in the course of the centuries, and…what stands behind and above these symbols is unaffected by such changes.

Just like scientific measurements, each individual religious conception is esoteric and assailable; but taken together, we can—through a leap of faith—infer the existence of some underlying driving force.


So Planck sees religion and science following a similar pattern: many different outward manifestations which, under analysis, point to a single absolute truth.

…religion and natural science…are in agreement, first of all, on the point that there exists a rational world order independent from man, and secondly, on the view that the character of this world order can never be directly known but can only be indirectly recognized or suspected. Religion employs in this connection its own characteristic symbols, while natural science uses measurements founded on sense experiences.

It’s this single absolute truth that drives Planck. But the idea that there are two absolute truths—one religious and one scientific—is clearly untenable.

Thus nothing stands in our way—and our instinctive intellectual striving for a unified world picture demands it—from identifying with each other the two everywhere active and yet mysterious forces: The world order of natural science and the God of religion. Accordingly, the deity which the religious person seeks to bring closer to himself by his palpable symbols, is consubstantial with the power acting in accordance with natural laws for which the sense data of the scientist provide a certain degree of evidence.

Planck accepts that the methods of science and religion are radically different. Religion begins with a belief in the Absolute, and derives its myriad symbols and rituals from it; science begins with empirical knowledge, and derives its belief in the Absolute from a broad agreement in experiments.

And yet they still operate with the same objective.

…the two roads do not diverge; they run parallel to each other, and they intersect at an endlessly removed common goal.

There is no better way to comprehend this properly than to continue one’s efforts to obtain a progressively more profound insight into the nature and problems of the natural sciences, on one hand, and of religious faith on the other. It will then appear with ever increasing clarity that even though the methods are different—for science operates predominantly with the intellect, religion predominantly with sentiment—the significance of the work and the direction of progress are nonetheless absolutely identical.

Mind and Matter

For Planck, Religion and Science are non-overlapping magisteria—they are equally valid ways of viewing the same reality. He refers to the apparent incompatibility as a “phantom problem”, a problem which is rooted in the inadequacy of language:

The room in which we now sit, has two side walls, a right-hand one and a left-hand one. To you, this is the right side, to me, sitting facing you, that is the right side. The problem is: Which side is in reality the right-hand one? I know that this question sounds ridiculous, yet I dare call it typical of an entire host of problems which have been, and in part still are, the subject of earnest and learned debates…great caution must be exercised in using the word, real. In many instances, the word has any sense at all only when the speaker first defines clearly the point of view on which his considerations are based. Otherwise, the words, real or reality are often empty and misleading.

Along these lines, Planck claims that there is a terminus of science, a boundary it simply can’t cross due to its point of view.

The scientist can look outward at past events, and infer the chains of causation that run through them. He might even look back at his former self, or at other scientists, and understand human behavior from the standpoint of causation. But the “here and now” is off limits—as he points out, “the most penetrative eye cannot see itself, no more than a working instrument can work upon itself.”

The fact is that there is a point, one single point in the immeasurable world of mind and matter, where science and therefore every causal method of research is inapplicable, not only on practical grounds but also on logical grounds, and will always remain inapplicable. This point is the individual ego. It is a small point in the universal realm of being; but in itself it is a whole world, embracing our emotional life, our will and our thought. This realm of the ego is at once the source of our deepest suffering and at the same time of our highest happiness.

Here Planck departs with the materialist view of contemporary science, which sees the mind as an epiphenomenon arising out of matter. And, despite believing the mind-body problem to be a “phantom” one, he champions the Idealist perspective: that mind is primary.

Asked by an interviewer, “Do you think that consciousness can be explained in terms of matter and its laws?”, Planck replies:

No. I regard consciousness as fundamental. I regard matter as derivative from consciousness. We cannot get behind consciousness. Everything that we talk about, everything that we regard as existing, postulates consciousness.

Planck seems to be alluding to a Spinozan or Schopenhauerian conception of reality, with the universe emanating from a singular Mind. In a later speech, he explains:

I would like to observe that my research on the atom has shown me that there is no such thing as matter in itself. What we perceive as matter is merely the manifestation of a force that causes the subatomic particles to oscillate and holds them together in the tiniest solar system of the universe…we must assume that this force that is active within the atom comes from a conscious and intelligent mind. That mind is the ultimate source of matter.

This sounds dangerously Pantheistic for a practicing Lutheran. But the conclusion springs directly from Planck’s union of the two Absolutes, of “the world order of natural science and the God of religion.” As we saw Planck state above:

the deity which the religious person seeks…is consubstantial with the power acting in accordance with natural laws

Belief and Knowledge

It’s important to note that Planck’s beliefs don’t rest purely on scientific evidence or rational logic.

In his writing, he acknowledges the rigor of the Positivist view—the idea that we can only trust first-hand experiences—but points out that it’s rigor makes it incredibly limiting. Any sensible view of reality requires a leap of faith, into a squishier, less rigorous world.

First-hand empirical knowledge only places constraints on our beliefs: we can’t reasonably claim to believe something contradicted by repeated experimental results. But reality is under-determined by empirical knowledge—there are many different potential beliefs, all compatible with what we know empirically.

Furthermore, there are moral, aesthetic, and practical reasons for adopting one belief over another. Here’s an exchange between Planck and an interviewer:

Interviewer: Do you think that life and consciousness are the outcome of the random action of natural laws, or do you think that they form part of some great scheme?

Planck: I believe that life is part of some greater life that we cannot understand. But this is not a scientific belief. It is a belief that must be justified on quite other than scientific grounds. Your question can only be answered by a fantasy.

Interviewer: A fantasy?

Planck: A fantasy is a way of representing things for oneself in other than scientific terms. The beliefs that are expressed in a fantasy are not amenable to scientific tests. They are beliefs of a different order from beliefs that rest on scientific evidence. Your question is not one that can be decided by bringing forward scientific evidence. Nevertheless it is a question concerning which beliefs may be held.

Interviewer: How are such beliefs to be justified?

Planck: By their influence on character. Such beliefs cannot be sincerely held without profoundly influencing character. A man’s character can be the outcome of such beliefs. And the resultant character is the justification or condemnation of the beliefs. This is the only way in which such beliefs can be judged. The scientific criteria of true and false cannot be applied to them. Moral and scientific beliefs are justified on quite different grounds.

Planck constructed his worldview in a pluralistic fashion. He drew from science, religion, and philosophy where appropriate, and saw none as inherently superior. And he had a stark understanding of the epistemic uncertainty that underlies all worldviews—including ostensibly scientific ones.

In both science and spirituality, he faced that uncertainty by adopting a steadfast faith that reality is ultimately reasonable—that all our disparate experiences can be explained by a singular, absolute Truth. Planck’s highest goal was to approach this Truth, by all available means. As he puts it:

Religion and natural science are fighting a joint battle in an incessant, never relaxing crusade against skepticism and against dogmatism, against disbelief and against superstition, and the rallying cry in this crusade has always been, and always will be: "On to God!"


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