[Topics: Anthropic Principle, Logic, Physics]
Tautological Wisdom:

The Anthropic Principle, Carl Sagan, and Accounting for the Simplicity of the Physical Laws


Carl Sagan Sketch by M.R.P. - The Dragons of Eden: Speculations on the Evolution of Human Intelligence - Brandon Carter - Anthropic Principle, physical laws

Caricature Sketch by M.R.P.


I should start by saying that I am well aware that Carl Sagan was not (in the strictest sense) a philosopher. His areas of expertise, as you may well know, were biology, physics, and mathematics. But he was a scientist who, unlike many of today’s most famous science advocates, had a deep respect for and interest in the humanities.

Indeed, in Sagan’s Pulitzer Prize-winning book on contemporary neuroscience and anthropology, The Dragons of Eden: Speculations on the Evolution of Human Intelligence, he writes (when concluding a section on the research results concerning the partial specialization of the two halves of the brain), “I think the most significant creative activities of our or any other human culture—legal and ethical systems, art and music, science and technology—were made possible only through the collaborative work of the left and right cerebral hemispheres” (Sagan 195).

And in that same book, Sagan references and engages with philosophical work by Plato, St. Augustine, Sigmund Freud, and Henry David Thoreau (among others). I have striven in this series to stress the need for mutual respect, mutual education, and even fruitful overlap between philosophy and science, and have upheld other individuals who endorse that confluence. Carl Sagan was one such individual.

Toward the end of The Dragons of Eden, Sagan engages briefly with the topic of the comprehensibility of the universe (in a passage from which I draw a lengthy quotation below). When I first read that part of his book, it occurred to me quite suddenly that Sagan, while not spot-on in my reckoning, was pointing toward a very promising low-level explanation for the seemingly remarkable notion that the fundamental physical laws strike us as mathematically simple—or at the very least comprehensible. In order to explain my interpretation of Sagan’s thought, I would like to first briefly discuss a closely related subject: the Anthropic Principle.

The Anthropic Principle by Analogy:

The Anthropic Principle is a twentieth-century consideration in physics (and soon after in philosophy) that intends to help handle the question, ‘Why does the universe possess the seemingly improbable necessary conditions to support life?’ as well as some related, more specific questions, expressions, and data regarding the age and laws of the universe. In order to explain this principle, which I intend to use as an analogy below, I will make use of a further analogy.

Asking the question ‘Why does the universe support conscious life?’ is like asking the question ‘Why did I win at roulette?’ The only answer that can be given is not the answer that is desired. The answer to the roulette question would involve the physics of the spinning apparatus, the physics of the released ball, and (depending on your model of consciousness) either the biochemistry of the brain as it made the bet or the state of consciousness that chose where to bet.

But that’s not the desired answer, as the desired answer, at least in the questioner’s conception, has nothing to do with physics, and just needs to account for the harmony between those first two elements (apparatus and ball) and that last element (brain).

Perhaps an aspiring answerer could get slightly closer to satisfying the questioner by showing that the statistics for winning at that particular roulette table on that particular day correspond to the theoretical statistics for winning a game of roulette, with some allowances for minor variations.

But that still does nothing to satisfy the questioner, whose question really boils down to the general form, ‘How can an unlikely thing ever happen?’ And to that question, the only answer of which I am aware is that, for a thing to be unlikely—rather than impossible—it must still be possible for it to happen.

The bickering could go on and on, as the questioner pedantically demands an answer to an endless string of follow-up questions, all beginning with the words ‘But why.’ And yet there could never be any satisfaction, unless some currently unfounded noncontingent explanation for the nature of reality lies at the end of the line of questioning, such as, ‘Magic did it.’

Similarly, one could pursue the presently existing harmony between the universe and life as far as they like—and I strongly support the efforts of physicists, astrophysicists, and biologists who are doing exactly that—but the ultimate answer to the question when it’s simply stated (as it was above) must be shaped by the notion that an observer is necessitated by the observation.

There is no version of reality where a person can make the statement, ‘There are no people here, just as the probabilities would predict.’ And this tautological notion, that an observation of the universe’s life-supporting conditions must by definition result from a conscious being in a universe possessing life-supporting conditions, is precisely the Weak Anthropic Principle as originally formulated by the physicist Brandon Carter.

The Anthropic Principle as Analogy:

With that in the background, now I would like to talk about an unlikely topic which arises in scientist and science educator Carl Sagan’s discussion of evolutionary biology in The Dragons of Eden: why the fundamental physical laws seem so amenably mathematically understandable to us. Sagan provides his own semi-serious possible answer to that concern when he makes the following remarks:

The laws of falling bodies seem simple to us. At constant acceleration, as provided by Earth’s gravity, the velocity of a falling object increases proportional to the time; the distance fallen proportional to the square of the time. These are very elementary relations. Since Galileo at least, they have been fairly generally grasped. Yet we can imagine a universe in which the laws of nature are immensely more complex. But we do not live in such a universe. Why not? I think it may be because all those organisms who perceived their universe as very complex are dead. Those of our arboreal ancestors who had difficulty computing their trajectories as they brachiated from tree to tree did not leave many offspring. Natural selection has served as a kind of intellectual sieve, producing brains and intelligences increasingly competent to deal with the laws of nature. This resonance, extracted by natural selection, between our brains and the universe may help explain a quandary set by Einstein: The most incomprehensible property of the universe, he said, is that it is so comprehensible. (Sagan 242-43)

Let me first dispense with the unnecessary and somewhat amusing comment that Sagan makes about “resonance” and “our arboreal ancestors who had difficulty computing their trajectories.” This strikes me as a definite misstep in Sagan’s reasoning. A person can (and many do) learn to play the guitar without understanding the physics of reverberation and sound waves. Similarly, there are many competent physicists who can not play the guitar. Expecting a species that is (intuitively) great at precisely jumping from place to place to have a better (conceptual) understanding of the physical laws than a relatively grounded species is quite a stretch.

But what strikes me in this paragraph as being productive of highly valuable insight is this sequence of thoughts: “Yet we can imagine a universe in which the laws of nature are immensely more complex. But we do not live in such a universe. [. . .] Natural selection has served as a kind of intellectual sieve, producing brains and intelligences increasingly competent to deal with the laws of nature.” In order to see the potential wisdom of this thought, one has to flip it around in the way that the Anthropic Principle flipped the question in the section above.

Here is the flipped (tautological) variant: any being who comprehends the physical laws of the universe in which it exists well enough to question why they are not more complex necessarily possesses the faculties to comprehend those physical laws well enough to pose that exact question. I might call this ‘the Intellectual Principle,’ because it takes a backward route toward explaining why some things are more comprehensible than others in much the same way that the Anthropic Principle takes a backward route toward explaining the seeming improbability of observed constraints.

The Dragons of Eden: Speculations on the Evolution of Human Intelligence book cover - Carl Sagan - Brandon Carter - Anthropic Principle, physical laws

The physical laws are comprehensible to us because, obviously, they are comprehensible to the sort of brains that humans have. At present we ask why multiplication is so utterly simple, why the physical laws are so comprehensible, and why quantum field theories are so complex. But if we were smarter (as we may be, some day), and able to understand quantum field theories without much difficulty, then we might instead ask why the physical laws are so utterly simple, why quantum field theories are so comprehensible, and why some partial differential equations are so complex. And if we were dumber (as we may have been, in the distant past), and unable to comprehend the physical laws with such aplomb, then we might instead ask why counting is so utterly simple, why multiplication is so comprehensible, and why the physical laws are so complex. The questions would change, but the concepts would not.

To put it another way, consider what it is for a concept to be simple. Recall, first, the trivial general point that a qualitative measurement is always a relative measurement. Something is small, for instance, only because it is smaller than some set or subset of an arbitrary reference frame. A large marble is a very small bowling ball. All this means is that, relative to those things humans consider to be complex (i.e. not easily comprehensible to humans at present), a simple thing is one that is not as complex (i.e. easily comprehensible to humans at present).

Now, perhaps you can start to see how the question of why the physical laws are simple may be somewhat malformed, or unhelpful. As in the case of the Anthropic Principle’s initial query, it is the kind of question about an apparently remarkable feature of reality that necessitates within its askability (more precisely within its asker, in the Intellectual Principle’s case) the feature about which it is asking. There is no version of reality where a person can both rationally and seriously say, ‘This concept no person can comprehend is remarkably comprehensible to people.’ Some things are comprehensible to us, and some things may not be; the physical laws more-or-less seem to fall in the former group for some people at this point in time, making their question superficially (and maybe only temporarily) meaningful.


So, the Anthropic Principle (technically, as used here, the Weak Anthropic Principle) is a way of thinking about how we think about the universe. Inherent to that statement of the principle is an awareness of the most common mistake that can be made on subjects like these: falling victim to the superficial impression that, because they are tautological, they are unimportant. But these are effective ways of more precisely considering some very big questions in science and philosophy. Both disciplines are quite often in the business of not only searching for answers, but also taking the time to properly refine the questions they ask.

Brandon Carter - The Dragons of Eden: Speculations on the Evolution of Human Intelligence - Carl Sagan - Anthropic Principle, physical lawsAs I went on to discuss, the pattern of thinking demonstrated by the Anthropic Principle also lends credence to Carl Sagan’s passing remark from The Dragons of Eden that we happen to live in a universe wherein the natural laws are the way they are, and happen to be at a point in the developmental history of human intelligence at which our perception of them is as being to some degree comprehensible.

As in the roulette case, what the questioner in the physical laws case really means to be asking is why there is a seeming harmony between the one element (our present mathematical expressions of the physical laws) and the other element (our brains). And, as in the roulette case, that questioner will be able to continually get arbitrarily closer and closer to the answer they seek (and may do so quite productively), and yet remain confused about their background assumptions and about the nature or even possibility of the answer being sought.

Work Cited:

Sagan, Carl. The Dragons of Eden: Speculations on the Evolution of Human Intelligence. Random House, 1977. Print.

[Topics: Anthropic Principle, Logic, Physics]
Tautological Wisdom:

The Anthropic Principle, Carl Sagan, and Accounting for the Simplicity of the Physical Laws

was last modified: May 12th, 2017 by Daniel Podgorski
Bookmark the permalink.


  1. In the concluding sentence of your opening paragraph, you say that Sagan “had a deep respect for … the humanities.” In one sense, this is true, and admirably so. Alas, in another respect, this is not true, and lamentably so. In the concluding chapter of “Dragons of Eden” (I think it was the last chapter, as my reading of the book was a long time ago), he sacrifices his own scientific (and philosophic) integrity — and humanitarian respect for difference — by dismissing all parapsychology as infantile nonsense, thus confirming his dogmatic empiricism, while inadvertently confessing his utter failure to explore the deeper recesses of the psyche. He had neither the courage nor the interest nor the discipline to engage in lengthy zen-like meditation, to become adept at dream recall, and to cultivate the art of lucid dreaming. Had he done so, his awe at the mystery of being and the miracle of life would have been greatly deepened, and he would not have succumbed to the temptation to take such a nasty and dismissive swipe at the possibility of parapsychological experience; and he might well have agreed with Kierkegaard’s conclusion that “you’ll never find consciousness at the other end of a microscope.” Socrates, Plato, Buddha, Meister Eckhart and William Blake were not, after all, total fools. Up until that last chapter, I enjoyed Sagan’s book immensely; but that last chapter showed how dogmatic, dismissive, and infantile Sagan himself could be (as are scholars like Daniel Dennett today). Knowledge does not become wisdom without deep self-exploration. Sagan could have been so much more evolved had he appreciated the deeper meaning of Kant’s assertion that “enlightenment is liberation from self-imposed immaturity,” Meanwhile, thank you for a lucid and provocative essay.

React to this Article