Lucretius, Of the nature of things
But, now again to weave the tale begun,
All nature, then, as self-sustained, consists
Of twain of things: of bodies and of void
In which they’re set, and where they’re moved around.
Ever since the ancient Atomists made the bold claim that nothing exists but atoms and void, we’ve struggled to understand the implications. For example, our immediate personal experience of the world says that our identity endures from day to day, even as we learn and grow and change. We have an intuition that ‘I’ exist in some essential way, a sensibility that atomism seems to undermine.
It is, of course, possible that we are more than the atoms that make us up, that we have, in fact, an immaterial soul that lives on after death. I’m not going to argue here against such a belief, which gives comfort to many people, nor will I make the dubious claim that science can pass final judgement on such matters. I’ve written elsewhere about the related quest for eternal truths in theoretical physics. But, I’ll note that the eternal life of the soul is not a comfort for everyone, and for some, like Lucretius, it’s our very mortality that gives life its poignancy and zest.
Instead, what I want to do in this short essay is explore how intuitions about the material world can bleed over into other areas, like ethics, religion, or politics, and in particular the ways in which the familiar atomist intuition about the ‘material world’, an intuition we think is scientific, is in fact very outdated.
Why is this important?
Even if we are not scientists, our intuition about how the world works and what we are made of helps to guide our thoughts in certain directions. These intuitions encourage us to take things for granted that in fact need to be examined and questioned.
For example: atoms move through the biosphere, forming and reforming the patterns we call living beings and non-living matter. The boundaries of the atomistic body are not sharply defined in space and time. We are eaters, and we are what we eat. We are drinkers, and we are what we drink. Or what we breath. These are truisms, safe grounds from which to start an adventure in free thought. Let’s pull on those threads, use our imaginations to see with the mind’s eye how we are networked with so much of the living world through our very bodies.
This view understands that every breath we take also contains at least a few atoms exhaled by the dying Caesar, or that some molecules of the water we just drank once churned through the beating heart of a blue whale.
Philosophizing in such ways is fruitful, playfully subversive without making grand metaphysical claims about the ultimate nature of things. It leaves open a world of possibilities and potential for discovery.
This way of understanding ourselves and our relation to our surroundings is also reminiscent of the philosophies of more traditional cultures, like that of Native Americans, which teach that the water of the rain, the lake, the river, and the ocean is the water of myself, so you have to keep that water clean wherever it happens to reside. It’s all part of one large flow, back and forth, in and out, the earth’s circulatory system.
Astronomers have even discovered that we are also part of a much larger and ponderous flow. Over cosmological time scales, supernovas mix and remix the materials out of which whole star systems are made.
Given the idea that we are permeable, and that the stuff we are made of is always changing, the question of personal identity now comes to bite us: What am ‘I’? Plutarch’s Ship of Theseus puts the question: if a ship is replaced part by part, at what point is it no longer the same ship? The same can be asked of us.
Our memories of ourselves may seem fixed, yet our current understanding is that those memories are encoded in the patterned arrangements of neurons, and ultimately the atoms, that make up our brains at any given moment. Those atoms change over time, with new atoms taking up locations that originally housed other ones, and so the neural patterns can endure, but over weeks and months, I am made of new stuff. At what point am ‘I’ no longer me?
This deep and weighty philosophical problem of personal identity was playfully explored by writer L. Frank Baum. The 1939 film, The Wizard of Oz, based on Baum’s Oz series of books, never reveals why the Tinman has no heart, but the earlier book, The Tin Woodman of Oz, tells his backstory. It’s complicated. Here’s a very brief synopsis:
The fully human Woodman, Nick Chopper, falls in love with a witch’s assistant and tries to steal away with her. The witch finds out, and she curses Nick to suffer one mishap after another, through bad swipes of his axe, and so his human parts are replaced with tin parts, one after the other. But,
“In the Land of Oz,” replied the Emperor [the Tin Woodman], “no one can ever be killed. A man with a wooden leg or a tin leg is still the same man; and, as I lost parts of my meat body by degrees, I always remained the same person as in the beginning, even though in the end I was all tin and no meat.”
All tin, except of course, for his heart, which was still missing when young Dorothy arrives. Now you’re caught up.
Baum takes the problem of Nick Chopper’s personal identity to extreme lengths in a scene where the Tin Woodman discovers his own (original) head in a cupboard, where’s it’s been hidden away by the witch. Startled, he asks the head “Who are you?”
“I used to be called Nick Chopper, when I was a woodman and cut down trees for a living.”
“Good gracious!” cried the Tin Woodman in astonishment. “If you are Nick Chopper’s Head, then you are Me—or I’m You—or—or— What relation are we, anyhow?”
Good question. Somehow the memories of his identity have been duplicated.
This memory duplication, and interrogation of personal identity, is a favorite trope for science fiction stories, too. Most of these stories are based upon intuitions about matter that the Greek Atomists would immediately grasp. Yet, in modern physical theory our atomism is even more radical than the Greeks’. The modern update to Atomist theory comes in several flavors.
For example, all fundamental particles of a given type, all electrons, or all photons, or all top quarks, are posited to be indistinguishable. This is a far stronger statement than simply saying they are ‘alike’. When counting the number of distinct microscopic states of a physical system, if we exchange electron A with electron B, those two states (AB and BA) are counted as the same state.
We need to count the number of microstates when computing physical quantities like entropy, which is essentially the log of the number of distinct microstates. This type of counting leads directly to measurable predictions about the behavior of large numbers of electrons (say in an electrical conductor) that are in agreement with experiment. Treating the two states (AB and BA) as distinct leads to predictions that are not in agreement with observation. 
This is very strange. If we swap an atom on one side of a room with an identical atom on the other side of the room, we only get to count those swap partners as one state. In fact, we have to swap every atom in the room with every other atom, in all possible combinations, and still count that as only one distinct state. The count of microstates isn’t changed by identical particle swaps. The collective microstate only changes if the position or velocity of one or more of the atoms is changed.
Furthermore, the nature of the atoms and the vacuum of modern physics is far more subtle, complex, and dynamic than the ‘atoms and void’ of the Ancient Greeks. Now add to this mix the additional strangeness of quantum mechanics, and dig even deeper into quantum field theory and the Standard Model, with its roiling vacuum and sea of virtual particles, popping in and out of existence in a restless dance, the forces between particles emerging from the constant exchange of other particles…well, it can become too much for the old-style materialist mindset to take in.
The theories just mentioned are the product of early or mid-to-late-twentieth century physics, and they now rest upon a firm experimental foundation, confirmed by many tests over the decades. The more recent theories of dark matter and dark energy, string theory and the multiverse, are still seeking confirmation, and these theories are wilder still. The Borges’ story The Garden of the Forking Paths is sometimes invoked to explicate the multiverse in literary form, for example. But it’s more evocative to imagine the story of infinitely forking paths as told from the center of a nuclear fireball.
The modern atomist revolution is still unfolding, and the radically different character of 20th century physical theory has not yet penetrated other areas outside the sciences, areas where some intuitions still seem based upon a 19th century style of thinking about the nature of matter, a theory which physicists found they had to abandon over a century ago. Meanwhile, the revolutions of the 21st century are only just beginning.
Why does this matter? Because, once more, our intuitions about the stuff the world is made of can pop up in surprising places, like political or religious ideologies, as a kind of metaphysical fog seeping into places where those ideas really have no place. Science, the shared and open enterprise to develop reliable knowledge about the world, can morph by degrees into the ideology of scientism by this type of move, a trick of the mind’s eye, where sloppy, outmoded, and lazy thinking is passed off as ‘objective’ and ‘rigorously scientific’.
Freeman Dyson makes this point eloquently:
“I recently attended a talk by a famous biologist. He spoke about two philosophical viewpoints which he called scientific materialism and religious transcendentalism. He said, ‘At bedrock they are incompatible and mutually exclusive.’ This seems to be a widely accepted view, both among biologists and Christian fundamentalists. I do not share it. I do not know what ‘materialism’ means. Speaking as a physicist, I judge matter to be an imprecise and rather old-fashioned concept. Roughly speaking, matter is the way particles behave when a large number of them are lumped together. When we examine matter in the finest detail in the experiments of particle physics, we see it behaving as an active agent rather than as an inert substance. Its actions are in the strict sense unpredictable. It makes what appear to be arbitrary choices between alternative possibilities. Between matter as we observe it in the laboratory and mind as we observe it in our own consciousness, there seems to be only a difference in degree but not in kind. If God exists and is accessible to us, then his mind and ours may likewise differ from each other only in degree and not in kind. We stand, in a manner of speaking midway between the unpredictability of matter and the unpredictability of God…”Freeman Dyson, Infinite in all directions, page 7-8 (1988)
Dyson was one of the leading theoretical physicists of the 20th century, one of the creators of quantum electrodynamics (QED), and for many years the Director of the Institute for Advanced Study at Princeton (where Einstein spent his last two decades). His views are his own, of course, and I suspect that his theological speculations are not widely shared among physicists, who mostly keep their thoughts on these matters to themselves. But, the point Dyson is making is one that I believe most physicists would certainly agree with: that the ‘atomism’ of modern physics is not the atomism of Leucippus, Democritus, and Lucretius. The matter of modern physical theory is not the kind of matter that forms the metaphysical ground of ‘materialism’ as that word is generally understood outside of physics. The Materialist Emperor isn’t wearing the clothes he thinks he’s wearing, and his head is encrusted with the barnacles of long-dead theories.
And so, we are like the Tin Woodman who, when confronted with his own self, realizes that the questions “Who am I?” and “What am I?” are deeply and fatefully entwined. Perhaps that’s the heart of the matter after all.
 In fact, electrons are even stranger than I’ve described. In that case, the state of a system is summarized by a mathematical object called the ‘wave function’, which has the property that if we swap any two electrons in the system, the wave function has to flip an overall +/- sign.
Image: The Wonderful Wizard of Oz, book cover by William Wallace Denslow [Public domain], via Wikimedia Commons.