“There are no atheists in foxholes.”

This phrase purports to be an empirical statement. Despite the practical problems, one could in principle determine the percentage of nonbelievers in the infantry and interview them under fire—when a random event could end their life at any moment—to see how many abandon their skepticism and pray for divine intervention.

An important point, though, is that the statement has nothing to do with the existence of a god. It concerns the conditions under which people display belief in a deity. Turn this around and consider the obverse statement: “There are no theists in science.” I would like to discuss some of the forms of religious skepticism one finds among scientists and consider the psychological appeal of—in contrast to the empirical evidence for—their disbelief.

Physicists

There have been studies comparing religious beliefs of academics in various disciplines with those of the general population. Around the world, there are country-to-country differences in the proportion of nonbelievers/skeptics. In general, scientists are several times more likely not to believe in a god than is the general public. Views vary among disciplines, though by substantially less than between them and the public. And often, physicists, biologists, and psychologists are high on the list of religious skeptics.

For physicists, one emotionally persuasive argument must be the incredible size of the universe—with estimates that keep expanding along with improvements in our ability to observe. A current ballpark estimate is that there are two trillion galaxies, averaging 100 billion stars each, and you may if you like multiply that by some number to estimate the even larger number of planets.

The notion that we are somehow special, on this little speck of a planet, in this particular galaxy, at this particular moment in the 13.8 billion-year history of the universe, strains credulity for many physicists. Furthermore, after about a billion years, the universe began to appear more or less the way it does now. Everywhere in the universe’s vastness that astronomers look, the same laws of physics seem to hold true. Thus, the false assertion that the universe is only a few thousand years old seems preposterous, as does the belief that during the prescientific eras on our planet—when key religious texts were written—miracles inconsistent with the laws of physics occurred.

Mathematicians

Mathematicians, like other highly educated people, are less likely to believe in a god than is the general public. But interestingly, they are more likely to believe in a god—or to be open to ideas about divinity—than physicists and other scientists. As a teenager, I planned on becoming a mathematician. And while I sometimes feel as if I have forgotten more math than I ever knew, I do remember the high school moment when, in a college math class, the teacher manipulated an already breathtaking equation and came up with e^iπ = -1. I nearly fell out of my seat. It was a complete surprise. My astonishment at the result was exceeded only by my amazement at its beauty.

The equation brought together in one place the abstract concepts of negative numbers (numbers less than zero), imaginary numbers (the square roots of negative numbers), and transcendental numbers (numbers that, with minor qualifiers, are not solutions of algebraic equations; π and e are the two best known transcendental numbers).

That equation confirmed for me (in my sixteen-year-old wisdom) the reason that mathematics was superior to science: e^iπ = -1 was true then, would always be true in the future even after humans had disappeared, and had been true before the first human ever existed. Science is messy—new observations can overturn the firmest beliefs—but the pure logic of mathematics revealed eternal truths, including beautiful ones such as e^iπ = -1, that could never be contradicted.

The way I see the world now is rather different. While the logical perfection of mathematics remains, its very perfection is what detaches it from the messiness of reality. Hence, to a scientist, mathematics is reduced to a tool—something to be used in pursuit of the real goal, understanding reality (as opposed to achieving logical perfection). It is this difference in perspective that suggests to me a possible reason that mathematicians are more likely to believe in a god than are scientists: mathematicians may be more open to the logical possibility of a god, while scientists may give greater weight to the low empirical probability that a god exists.

Biologists

It turns out that biologists have the lowest rate of belief in a god. Most likely, in parallel to the ways the laws of physics and the age and size of the universe discourage belief in a god for physicists, it is evolution that fosters religious skepticism in biologists.

Some religions have adapted to modern biological science by accepting that evolution is at its core. However, they have argued that evolution is a means for fulfilling some divine purpose, such as putting humans at the top of the food chain (though they might not phrase it this way). There are several positive results that occur when a religion accepts science as a separate area of inquiry rather than treating it as an enemy. The acceptance neutralizes political opposition to scientific inquiry and allows the religion’s members who wish to do so to become scientists without fear of being shunned.

Unfortunately, though, the central idea of evolution is that it is random—there is no purpose. Whatever life-forms exist now do so as a result of the innumerable quirks, disasters, and other environmental circumstances that occurred on planet Earth over the past four billion years. We and other species are accidents of history who happen to be around at this particular moment in time. To say, for example, that a god aimed a comet at the Yucatan peninsula 66 million years ago to kill off three-quarters of all animal and plant species, including the dinosaurs, so that we could evolve from tree shrews strains the credulity of biologists.

Psychologists

Depending on your point of view, psychologists’ primary reason for religious skepticism, compared to those I’ve already mentioned, can be seen as either the most superficial or the most profound. From the points of view of physicists and biologists, psychologists have no comprehensive theories to match general relativity, quantum mechanics, or evolution. Nor do they have the scope of observations concerning the age and size of the universe, the world of subatomic particles, or the history of life on our planet. In this sense, psychologists’ skepticism about the existence of a god is a superficial one.

On the other hand, if there is one implicit message that psychologists receive and transmit throughout their education and careers, it is that subjective experience, while a fascinating object of study, is not a reliable indicator of objective reality. Nineteenth century psychophysics experiments explored the lack of correspondence between physical stimuli and the sensations they evoke. For example, there is not a straight-line relationship between the weight of an object and how heavy it feels or the brightness of a light and how bright it appears. The study of several optical illusions also has a long history. Visual illusions, from figure-ground reversals to mirages, similarly show that an unchanging visual stimulus can lead us to see different things that vary from moment to moment, and also that we can both not see things that are there and see things that are not there. Furthermore, we have instruments that measure sights, sounds, and other stimuli that human sensory organs are inadequate to detect. In other words, our sensations and perceptions do not necessarily reflect objective reality. The entire field of abnormal psychology deals with unusual thoughts, feelings, and behavior, and much of psychiatry involves the use of drugs to change subjective experiences such as sadness or hallucinations.

In short, psychologists are inclined to view religious experiences as interesting subjective phenomena unrelated to the existence of a god or other supernatural phenomena. For example, out-of-body experiences—which are rare but well-documented phenomena—have been used as evidence for the existence of a soul. Believers contend that whatever entity it is that leaves the body during an out-of-body experience might be able to continue an existence after death. Early in this twenty-first century, however, it was discovered that out-of-body experiences result from a disturbance in functioning of the temporo-parietal junction in the brain. That is, they are subjective experiences, but there is no entity that actually leaves the body.

This is the sense in which psychologists’ skepticism about a god is seen as profound. If the experience of a god or other religious phenomena is all there is—just transitory subjective experience, rather than evidence for the eternal existence of a god or an afterlife—then there is nothing substantive to believe in.

People can enjoy their religious experiences, including the experience of a god, if and when they have them—the way they enjoy a piece of music or a painting—without needing to believe that a god actually exists or to view their experience as a better indicator of reality than science. This enjoyment is similar to (if more intense than) the way we can appreciate a video depicting objects moving in ways inconsistent with gravity without seeing the video as challenging the laws of physics.

A Parable

On a religious note, I close with a parable, probably apocryphal, told about Albert Einstein.

An acolyte asked the great physicist, “Tell us, Dr. Einstein, why is it that we try to understand psychology in terms of biology; we try to understand biology in terms of chemistry; we try to understand chemistry in terms of physics; and we can only understand physics in the language of mathematics?”

“That,” replied the sage, “is a question for a psychologist.”