A Fabulous Evolutionary Defense of Dualism


Ah, dualism. It sounds so remote and academic. The kind of thing gowned philosophers might debate while strolling the quad. Sure, dualism is a deal more rarified than “bracketology”—the study, according to ESPN, of who is going to win the NCAA basketball tournament.

Bracketology is huge to people who bet on March madness. The FBI claims that more than $2 billion changes hands during the course of the tournament. That’s a ton of money, but believe me a lot more rides on the outcome of the dualism debate.

Broadly speaking, dualism is the proposition that the universe is composed of both material and immaterial stuff. Traditionally, the immaterial stuff makes up the mind or soul—in contrast to the material brain or body. We all (so far as I know) possess an unshakable feeling of having a mind, and many of us sense a soul within the skin. On the material side, however, I don’t know about you, but I’m generally unaware of having anything inside my head—except perhaps on a morning after I’ve drunk too much. That’s when I know I have a brain, and it’s the size of a walnut.

Nevertheless, outside theological circles dualism is far from fashionable. From physics to neurology, science has gnawed away its foundations. This might seem like an arcane quibble, but it should be of grave concern to anyone hoping to see science and religion reconciled.

Here’s why: If physical stuff is the only kind of stuff that’s real, what’s left for religion? Apart from a relatively few people who worship nature itself, no religion I am aware of could be content with this worldview. After all, nobody believes that God is made of molecules, right? That would make God subject to the laws of physics.

However, just to stipulate that God is transcendent doesn’t resolve matters. The very arguments against mind/brain dualism form potent objections to any claim that God acts in the world. Take the First Law of Thermodynamics, better known as conservation of energy. Monists (those who argue that physical stuff is the only stuff there is) point to this law to argue that if there were an nonphysical mind it would be unable to influence the brain without injecting some energy into the world. (Brains, being made of matter, can only react to energy.)

However, to add energy from the Great Beyond would violate the conservation law. We don’t have to be physicists to imagine how readily evident that would be. No matter how small, the extra energy streaming from mind to brain would pile up and eventually be measurable. No such excess of energy has ever been found.

To the contrary, a huge body of evidence demonstrates that the conservation law holds here, there, and everywhere. Therefore, crows the monist, to claim that there is a mind as pointless as insisting that there is an invisible dragon in Carl Sagan’s garage.

The idea of “an immaterial spirit that occupies individual brains,” says V. S. Ramachandran, director of the U.C.S.D. Center for Brain and Cognition, “is complete nonsense.”1

What goes for minds and souls goes for God, unless we want to fall back on magic. It’s not for me to tell God how to get things done, of course, but to go that route is to give up, perhaps prematurely, on a rational reconciliation of claims. Can it be true that the laws of physics hold, and that God acts in the world?

I think so. And I think evolutionary biology (with a dash of physics) can help us see how.

In fairness, though, I must confess up front that my version of dualism allows only a narrow channel of interaction. I am not about to argue for the reality of the Noachian flood or the Immaculate Conception. Miracles, if any there be, are by definition beyond rational explanation.

The Case Against Dualism

The monist position is, in sum, that the environment provokes nerves to fire and their signals reach the brain, causing a certain sequence of neurons to fire, with consequences. And that’s it. The whole chain of cause and effect is sealed within the laws of physics, which do not allow for interference by nonphysical forces. The mind, subjective self, and free will are therefore epiphenomena, illusory byproducts of the system with no causal influence over it.

In light of your experience, this may sound ridiculous. After all, you know that you have free will. You can hold your breath or stand on your head, if you choose. However, your experience also tells you that the Earth is standing still at the center of a revolving Universe. Centuries of careful observation and deduction force any reasonable person to conclude that the Earth spins on its axis at roughly a thousand miles an hour (at the equator). From this and many other instances, we know that experience can be unreliable.

Common sense alone is not a sufficient answer to the very powerful arguments in favor of monism. Before we defend dualism, we have to be sure we understand why it is so hard to defend. Here are some of the key arguments against it.

  • Interactionism: in principle, there is no conceivable way for a ‘ghost’ to have a physical effect without violating the law of conservation of energy; thus ruling out an immaterial ‘mind’ from influencing physical outcomes


  • Incoherency: proponents of dualism are unable to describe what they are claiming in a clear, consistent way. How can the reality of something be judged if it cannot be described?


  • Extravagance: the principle of Occam’s Razor calls on us to leave out anything not critical to an explanation of phenomena. It is sufficient, for example to explain a pot of boiling water to invoke the fire that heats it, rather than invoke an angry water god. Similarly, if physical principles can explain the interactions of the brain and world, enough said!

These arguments carry great weight, because without the mindset they represent we would not enjoy the tremendous advantages science has given us in the last 500 years. The great advantage of reducing explanations to physical principles is that they transcend all cultures and join in a coherent body of knowledge.2 Sadly, while nearly everyone appreciates at least some of the fruits of science, comparatively few people appreciate how it depends on a willingness to set aside the transcendental temptation in describing the natural world.

In my past writings I have often criticized those who attempt to have it both ways: to entertain a worldview that accepts science and hold onto their favorite supernatural proposition. I’ve battled the claims of the Intelligent Design movement, and I’ve dissed the idea, espoused by the biologist Kenneth Miller among others, that you can embrace science and miracles. Having taken this stand, I must be scrupulous to avoid giving into the transcendental temptation, not only for my sake (who wants to be a hypocrite?) but also because I believe it is crucial for humanity to relinquish magical thinking. And yet, I repeat, my task here is to uphold both the laws of physics and the proposition that God acts in the world.

So, from this standpoint how can we defend dualism? It seems to me sufficient to rely on three arguments: that nature points the way, that a ‘modeling’ model can meet the monist objections listed above, and that scientific evidence demands that we admit immaterial concepts into our world of “real things.”

What Good Is a Brain?

Evolution provides a great springboard for diving into these deep philosophical waters. It prompts us to ask what a brain is good for and what it costs an organism to maintain it. You might think that the utility of brains is self-evident. They allow organisms to extract information from their environment and react to it. But you don’t actually need a brain to do that. Even the tiny Rhodospirillum rubrum, a purple bacterium with no more brains than a doorknob, can sense light and corkscrew its way toward it.

There’s nothing mystical about such automatic responses. We build machines with such features all the time. When an elevator “senses” that someone has pressed button number 7, off it goes to the seventh floor. Elevators, however, cannot consider the advantages of going to the tenth floor instead—at least not yet. (Fans of the late Douglas Adams’ Hitchhiker’s Guide to the Galaxy series know what horrors await when elevators are installed with cyberpersonalities.)

Perhaps the extra value that a brain like ours provides lies its ability to manipulate the information it collects from the environment and model alternative futures. It’s an ability we evidently share with a number of animals. Consider a cat.

If you’ve ever watched a cat for awhile, you’ve probably seen something very much like this: the cat is pussyfooting along when she spots something interesting up on a countertop. Maybe it’s a bug crawling along. She hunches, focuses, and then rocks back and forth. She might rise out of her crouch for a moment then settle back down. At that stage, you just cannot tell whether the cat will spring or not. What’s going on? Surely, she is modeling consequences of her proposed leap and weighing the risks.

Cats are risk takers, so most likely she will make the leap. Perhaps she’ll make it, or perhaps she’ll flail and tumble back down to the ground. Either way, she’ll learn from the experience. That’s largely what a brain is for—modeling the future based on experience and real-time sensory data, and then making a decision. But if a cat’s brain is enough to do the job, why do we come equipped with a prefrontal cortex and all the latest and greatest in consciousness-generating machinery?

The Cost of Consciousness

Keeping up a brain that can do everything from regulating heartbeats to wondering about consciousness is a costly undertaking. It soaks up about 20 percent of the body’s oxygen supply—ten times its share by weight. Moreover, the human brain is so big that it makes birth exceptionally difficult. Women’s hips are as broad as they can be and still allow bipedal locomotion. The tragic consequence is that, without modern medicine, an appalling number of mothers and babies die in childbirth.

That creates negative selection pressure, which must mean that there is an even greater opposing selection pressure in favor of big brains. What could explain that pressure? One possibility, espoused by evolutionary biologists such as Geoffrey Miller, is that the human brain’s extravagant abilities are the result of sexual selection.

The argument is that, just as peacocks have evolved huge, unwieldy tails at the behest of picky peahens, so human courtship has resulted in the evolution of brains capable of generating music, art, morality, and above all elaborate symbolic language. It is a claim with considerable merit, but there are some obvious differences between the peacock tail and the human brain.

For one thing, the peacock’s tail is a dimorphic trait, meaning that, like beards in humans, it appears only in the male. Differences between male and female brains in humans are miniscule, and vanish altogether in proportion to the difference between the human and hominid brains. This is a pretty strong clue that human brains are more than mere ornaments.

In fact, human evolution traded away a lot to get such powerful brains. For starters, we gave up strong jaws. Imagine what a sacrifice that was at a time when our ancestors were hunter-gatherers. Very little of the available food was easy to eat. There was no mac and cheese, no ice cream, no jello. Hominids had to tear the raw flesh off bones or grind their way through tough grasses and roots.

Around 2 million years ago, a mutation in a single gene in one of our ancestors blocked production of a protein called MYH16, which is critical to the formation of strong jaw muscles, such as those found in gorillas. That kind of muscle requires a massive bone on which to anchor itself. Until the moment of mutation, every one of our ancestors had a thick skull with a big ridge of bone on its crown. The ridge served as an anchor for the jaw muscles. Once the mutation made its way into the gene pool, individuals who had carried it had no need of the ridge. They must have had a hard time keeping to the traditional hominid diet, but perhaps they found new food sources that served even better (termites, anyone?).

In any event, we know they survived, and we know they kicked off a rapid increase in brain size over the next several hundred thousand years. Liberated from the need for a crowning ridge, our ancestors evolved from boneheads to brainiacs. The liberated brain must have proved adaptive: all the brawnier hominids petered out and we’re still here. That would be unlikely if our big brains were merely for showing off.

The peacock’s tail is also more than mere ornament. It comes under a category known as the handicap fitness display. The huge, useless tail is a burden that only a truly fit peacock can bear up under. Of course, the extra capacities of human brains may well serve in courtship—ask any Elizabethan poet you can happen to meet – but they evidently serve many other ends as well. That would be typical of evolution, Nature’s ultimate multifunction designer. Look at the mouth: It’s not just for eating and drinking anymore! It also works for breathing, speaking, kissing and whistling, to name a few uses. Similarly, our brains are definitely multipurpose organs

So, it is difficult to see how natural selection could favor the kind of brains we carry around if costly features such as consciousness, conceptualization, and free will were merely illusory extras. In that case, even a cat brain might be too much. Ants seem to fare pretty well on about 1/40,000 the amount of brains we carry around.

Still, it’s important not to make a straw man of the monist position. There are certainly many who believe that mental features play a role but maintain that they can all be explained as brain states within a deterministic framework. There are others, a minority led by the mathematician Roger Penrose, who believe that the brain exploits quantum indeterminacy to free itself from the harness of classical physics.

The Joke’s On Us

We’ve summed up the monist’s case. What supports the dualist? There is the evidence of consciousness and its powers. Just because their validation might spoil the current scientific paradigm is not reason for rejection. After all, quantum mechanics sank the determinism of classical physics, but the evidence wins.

So let’s look at consciousness through an evolutionary lens. As anyone who has ever experienced one will tell you, a conscious experience is radically different from mere knowledge. Let me demonstrate:

The teacher, noticing that little Billy doesn't seem to be paying attention in history class, suddenly asks, "Billy, can you tell us what happened when Hannibal crossed the Alps with his elephants?" Coming out of a daydream, Billy ponders a moment and then says, "Oh, I know! He got a mountain range that never forgets!"

My computer has now stored this joke, but I’m pretty sure it doesn’t get it. Even if I programmed in heaps of data about mountains, elephants, and idioms, it still wouldn’t be amused. Hopefully, you were, and even if you weren’t you can remember what it feels like to be amused. It is an experience that defies reduction to brain states, even though it remains dependent on them. It is moreover, a gift from evolution, one of the human universals.

Amusement and other qualia, as philosophers call them, are subjective experiences that have as yet no satisfactory scientific explanation. At best we have speculations about recursive brain functions that give rise to self-awareness.

However, our brains are aware of more than just the physical environment and self. They are jam-packed with concepts that embody abstractions, fictions, and contradictions with no physical object.

Take Spongebob. Although he purportedly resides in Bikini Bottom on the floor of the Pacific Ocean, Mr. S. is clearly a fictional character whose relation to any living creature, marine or mammalian, is tangential at best. In Spongebob Squarepants, then, we have ready proof that human brains can model nonphysical objects.

The monist may object that fictional characters are mere epiphood for thought. I disagree, and will now offer an evolutionary fable to make my case.

You and I have a great grandfather in common. Most likely he lived in Africa some hundreds of thousands of years ago. Let’s call him Olujimi,3 or Jimi for short. Picture Jimi sitting by a campfire in the grasslands when a lioness bursts into view. Like anyone of us, I am sure, he would run for his life. To do this would require nothing more than his brain recognizing the smells, sounds, and above all images reaching it as “lion!” and going into flight response.

Later, however, Jimi remembers the lion and imagines different outcomes. He models a wholly different response – what if he had picked up a burning branch from the fire and waved it in the lion’s face? He imagines the various possibilities and decides the most likely is that the lion will retreat.

Next time a lion shows up, Jimi puts his plan into action and it pays off bigtime. Not only does he survive, but all the women in the area think, “Wow! Here is a brave and clever man who can protect me and my offspring from lions! I think I’ll have his babies!”

Jimi becomes the happiest man on the veldt … at least until other guys catch onto his trick. Then, it’s back to the drawing board of the imagination to try to come up with some new competitive advantage.

Now, I hope you will agree that this is a highly plausible fable. Something very much like it surely happened at some point, and the use of conscious modeling of alternate futures has never stopped. In contrast to evolution, it is the chief engine of human innovation. Consciously driven innovation could not possibly occur, however, if there were no causal link between a concept and the world.


How could this take place without violating the laws of physics? I suggest it happens through the physical process of modeling. The perception of a real lion presents no problem: physical stimuli – mainly sound and light waves—lead to certain sequences of neuronal firing, which causes Jimi to jump up and run.

Similarly, the remembered lion is physically accounted for by the firings of neurons assigned to memory. The internal dynamics of a brain simulation may not be understood all that well, but our ignorance does not imply magic. We can assume that in modeling one thing leads to another, ending in a changed memory, which can later be used to drive a particular set of actions. Notice, however, that there must be some top-down causation going on, as coalitions of neurons embodying some idea (“wave burning stick”) shape the behavior of the next coalition of neurons actions (“laugh triumphantly at fleeing lion”).

This all may seem right, but we must guard against accepting intuitions. The monist may yet argue that consciousness and will are epiphenomena, and that the real action happens out of sight. Is there any evidence to support the claim that concepts can have consequences? Once again evolutionary biology comes to our aid.

The genetic code is the best example we have of the power of information. Some—myself included—have wondered if the DNA-RNA-protein sequence truly involves information in the deep sense. It might be argued that it is simply a dynamic process, sort of like a row of dominoes in which each one tips the next.

However, a series of experiments has blown any such notion away. It turns out that genes can embody high level abstractions such as “do what it takes to form an eye.” Pluck out the Eyes absent gene from a mouse and insert it into the genome of a fruitfly whose eyeless gene is missing, and you get a fruitfly with eyes.4 Not mouse eyes, mind you, but fruitfly eyes, which are built along totally different lines. A mouse eye, like yours or mine, has a single lens which focuses light on the retina. A fruitfly has a compound eye, made up of thousands of lenses in tubes, like a group of tightly packed telescopes. About the only thing the eyes have in common are that they are for seeing.

What does this tell us? Information, organized into concepts, is demonstrably out there in the world, and without violating the laws of physics it can guide processes as they unfold. As in the genes, so in the mind.

Discovering the Immaterial

Now comes the crucial step. If the environment that humans occupy contains not only material realities but also immaterial ones, can we then infer that human consciousness exists to discover and exploit these objects? Again, evolution suggests that this is so.

I hear Occam’s Razor stropping, so before I get my throat cut let me hasten to add that I’m not referring to ghosts or Spongebob but to objects whose power in the world is far more evident: numbers.

I suggest that we discover numbers and their relations by modeling them in our brains—or in clay tablets, notebooks, and computers.5 Moreover, I call on the increasing body of evidence that our brains are evolved not only for arbitrary human language but also for the universal language of math.6 The transcendental quality of math can be framed in cultural terms, but it cannot be denied. A prime is a prime, whatever symbols denote it.

In his marvelous book A Mathematical Mystery Tour, A.K. Dewdney makes an extended case for a strong form of mathematical realism. He argues (through a series of fictional interlocutors) that numbers are not only real but that they occupy their own realm, to which he gives the delightful name holos. The holos, in turn, gives rise to the cosmos, which, he rather convincingly argues, is dependent on equations, some of which humans have discovered. Equations, one of his characters argues, “provide all the information you could want about a hydrogen atom. There is nothing else, in effect. You could even say that not even the energy is real. Only the information about its behavior is real.”7 This is similar to the physicist John Wheeler’s claim that information is fundamental, summed up in the quip, “it from bit.”

I don’t know for sure whether this is true, but all of physics for the past one hundred years points in that direction. Yes, I know, if you run headlong into a brick wall you quickly discover its unyielding physicality. Nevertheless, in thinking of it as solid we misapprehend. In 1995, exactly 100 years after Einstein launched the quantum era, Eric Cornell and his team at the University of Colorado demonstrated the evanescence of atoms by creating the world’s first Bose-Einstein condensate (BEC). Rather than yield all of their information, a group of supercooled rubidium atoms disappeared into a blob of indeterminacy. It was—and still is—an astonishing confirmation of Nature’s insistence that you cannot know all about the position and momentum of a particle.

Consider: temperature is purely relational. The atom is only hot if it is belly bumping with other nearby atoms. How does it know when it has cooled to the point that it is time to merge into a BEC? Apparently, when its information slip begins to show. What Nature seeks to veil is not the structure of the atom but the relational information about it and its neighbors. Apparently, we can know all about the dancer but only so much about the dance.

Bringing Home the Bacon

So, relying on the inductive methods of science, as recommended by Sir Francis Bacon, we have compiled evidence for the following: that immaterial concepts inhere in the world, that they influence physical processes, that such concepts exist in the mind and work through the brain, and that the interplay of information and physics may be the most fundamental level of reality we can apprehend through science.

Many mysteries remain. We have at least established a modest dualism on a foundation stone of evidence. Information is immaterial yet real and powerful.

Where does God come into it? Here I must throw off my own veil. I am an agnostic who accepts that God is real to this extent at least: it is overwhelmingly evident that God is a powerful concept working in the world through the minds of believers. The monist may not like it, but to deny God in this sense is to deny the power of concepts altogether, and that, I think, we have shown to be unreasonable.

As to the deeper reality of God, that is a question of faith. For me, God is a mental construct in the minds of others. For you, perhaps, God is infinite, loving, and immanent. So be it. The discovery that there is more to the world than mere physics allows us to be both scientifically informed and at peace with our worldviews. How wonderful is that?


1 Quoted in Cornelia Dean, “Science of the Soul? ‘I Think, Therefore I Am’ Is Losing Force,” New York
, June 26, 2007.

2 The sciences form a nearly seamless stack of explanations. Pictured as a column, physics forms the pedestal, chemistry the trunk, and biology the capital. Other sciences, each with its own interesting questions, are located alongside. However, the column has three major gaps, two at the top and one at the bottom. At the top is the problem of consciousness (encompassing mind, will, and other issues that we are considering here). Between biology and chemistry, the problem of life’s origin remains open. At the base is the question of how to fit general relativity together with quantum mechanics, a problem that has led to the conjecture of supersymmetry.

3 A Yoruba name meaning “Gift of God”

4 These genes get their nicknames from the function that goes missing when they are excised. Each is crucial to eye formation in their species. See, for example, Nancy M. Bonini, Quang T. Bui, Gladys L. Gray-Board and John M. Warrick, “The Drosophila eyes absent gene directs ectopic eye formation in a pathway conserved between flies and vertebrates,” Development (1997) 124, 4819-4826.

5 The debate about whether numbers are invented or discovered is an old one, and I have made my own stand on this elsewhere, but I must repeat one point: if numbers and the rest of mathematics are inventions of the human brain, it follows that they are wholly dependent. It would therefore be no more true to say that the circumference of a Euclidian circle is 2Πr than to say that the name of the third planet is Earth. That equivalence seems unlikely to me, but the key point is that if this is so then logic, which is inseparable from math, is likewise merely conventional. I therefore argue that it is rational to accept (provisionally) that numbers are real in order to preserve the foundation of rationality itself. Otherwise, all knowledge becomes the plaything of rhetoric and power.

6 For an interesting journalistic report on number-brain research, see Jim Holt, “Numbers Guy:

Are our brains wired for math?” The New Yorker, March 3, 2008. www.newyorker.com/reporting/2008/03/03/080303fa_fact_holt?

7 A.K. Dewdney, A Mathematical Mystery Tour. New York: John Wiley & Sons, 1999. p. 146.

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