A View from the Shadows: The Allegory of the Cave

Plato’s “Allegory of the Cave”. This drawing is by Markus Maurer.

Plato’s “Allegory of the Cave” could almost, taken at face value, be the plot of a movie in the “Saw” series [1]. Prisoners in a cave, born into chains and forced forever to face a single wall, know nothing of the reality of what lives behind them. A fire somewhere behind the prisoners cast shadows that play on the walls. Our poor prisoners try to make sense of the reality of the world behind them merely through interpreting these shadows, never able to turn as see the world as it truly is.

It’s has the potential to be a terrible image, but softened a bit it can be a useful metaphor for thinking about what it means to use scientific inquiry to understand the reality of the cosmos. When we discover something using scientific inquiry and describe it mathematically, is that mathematical statement one approximating reality or truly describing reality as it is?

That question aside, Plato himself was not big into what we would now call “science” – in fact, he held many core beliefs that suppressed scientific thinking. In this post, another personal journey into “Reality in the Shadows,” I reflect on the satisfaction of wresting this metaphor our of Plato’s hands and giving it to a new generation. It is my hope that such a generation might only ever know the tools of scientific investigation for use in understanding the natural world. The world is filled with shadows, crying for explanation; I hope a new generation can appreciate how the tools of science can be used to make sense of those shadows in a reliable and reproducible way.

Frank, Jim, and I use the “Allegory of the Cave” as a central uniting theme of our book, “Reality in the Shadows.” It is a metaphor for how humans, with our limited senses and perspective, try to make sense of the universe. We are born on this earth, chained (in a sense) to its dry land, and yet curious about what casts the shadows we call “reality.” Our best method for doing this, science, has not answered every question… but it has helped reveal some of the forms that cast those shadows.

A scanning tunneling microscope image of silicon atoms. Not only can you see the wave nature of atoms revealed, you can see defects (missing atoms) in this crystal of silicon.

For instance, we cannot see atoms. They are too small, and visible light is insufficient to allow us to ever see them with our eyes alone. However, in many other ways we can see the consequences of atoms. From those we can infer atomic properties and describe those mathematically. From the mathematics, we can make predictions about things we’ve not yet observed. We can test those predictions, and if they are verified then we begin to accept our newfound understanding as a representation of the actual truth, whatever that may be. This kind of truth we call scientific truth, and while it may not sound as satisfying as “actual truth,” it is scientific truth that has made possible all the benefits of the modern world. Such truth has catapulted humans toward the stars and revealed previously unknown facts about the history, structure, and even possible fates of the cosmos.

For those of you who know something about the person of Plato, especially his beliefs about how one should make sense of the universe, the use of the “Allegory of the Cave” should seem a delightful irony. Carl Sagan makes much of this in his series, “Cosmos.” In many ways, Plato and many of his contemporaries can be seen to have held back civilizations, those based on Greek culture, by at least hundreds of years, stalling scientific progress (that otherwise went on to flourish for a time in cultures elsewhere, such as in Persia or China).

A crop of the painting “The School of Athens” by Raffaello Sanzio, 1509, showing Plato (left) and Aristotle

Plato held that one could understand reality merely by thinking about it. One did not need measurement or evidence gathered from the world; one needed only to interrogate the universe through pure intellect to understand reality. Plato was exceptionally influential, as was his teacher, Socrates, and his own student, Aristotle. While they cherished human thought, they held thought itself above material evidence that might, for instance, contradict a conclusion reached solely by the mind.

In many of his works, and especially in his most famous work, “The Republic,” Plato (writing this as a dialogue led by his teacher, Socrates) speaks out against the idea that, to assess reality, one must interrogate the material world. Rather, he asserts that the mind offers a connection to some spiritual world of unseen insights, and that it is therefore from the mind that actual truth arises. While this may seem comforting, placing the human mind at the center of the universe, it ultimately leads to nowhere by itself. Indeed the mind is important, but evidence gathered from the natural world is a crucial ingredient in assessing the natural world.

How can we understand this? Let’s choose an oversimplified example, but one that has the key distinctions made clear. One can imagine anything one likes. But as we know from experience, that doesn’t make our beliefs about the material world true (or false). For instance, I can imagine that I can leap unaided off of a building and fly, but the history of every person who’s ever tried this is that the only way is down toward the center of the earth. I suppose Plato might rail against my purely materialist view of the reality of gravity and its relentless pull, but I wonder if he would have taken a serious bet about what would happen to him should he leap off a building, even while having convinced himself through rational thought alone that he could fly?

In contrast, scientific inquiry takes the world as it is and tries to make sense of the relations between things that are. The world may seem (and, in fact, may simply be) a collection of facts, but facts alone are very boring. The fact that water has a density of 1 gram for every cubic centimeter of iteself at standard temperature and pressure doesn’t tell me anything about the why of this number. Why does it have this density under these conditions? What would happen if I increased the temperature of the water, or decreased it toward freezing? That original fact itself gives us no information. On its own, a fact merely is.

On the other hand, a material description of water as a collection of molecules made from hydrogen and oxygen, whose structure and behavior are based on the mathematics of quantum mechanics and electromagnetism… now that gives us a fuller understanding of water and why it will do what it will do. But that description is based on thousands of material observations that over centuries were converted into a theory. A theory, in the scientific sense, is an explanatory framework that incorporates pre-existing facts, observations, inferences, and mathematical explanations, but goes further than any one of those things or even their simple sum. Scientific theories predict new facts while explaining old ones… and that is what makes science so useful. Thinking about water, by itself, got us nowhere for almost 2000 years after Plato. Interrogating matter (which is what chemists did starting in the Renaissance) got us to the current stature of our collective human intellect and technology in just about two hundred years.

My personal view of our use of Plato’s allegory is this: it’s a good metaphor for how we think the universe might be, versus how we can actually describe it (no matter how reliable that description may be). But in using it as the heart of “Reality in the Shadows,”  we are in fact employing tools and ways of thinking ironically shunned by Plato himself. Plato embraced mathematics, for sure, but not observation and experiment.

As co-authors of this book, I don’t think any one us individually did this with the intent to frustrate or embarrass Plato – at least, speaking for myself, that certainly wasn’t the goal. The allegory of the cave really is an excellent metaphor. But, I would say that because we know the scientific method actually makes progress in understanding the shadows that play on the cave wall, we embrace the metaphor but take it beyond what Plato himself would have wanted. Science has given us some reliable ideas about what realities lurk behind us, though we are far from completely understanding that reality.

In many ways, modern scientists are inadvertently sticking it to Plato with their successful methods. Thus, for me, it was deeply satisfying to wrest this metaphor our of Plato’s hands and turn it over it to a new generation – to you – whose understanding of the universe is based, not on the pure thought of Plato, but on the best way of knowing ever established by humanity: scientific investigation.

References and Notes

[1] With apologies to Prof. Allan Silverman, the instructor of my university first-year introduction to philosophy. I am sure he never intended the allegory of the cave to be equated to an elaborate scene from a “Saw” series movie.

About “Reality in the Shadows”

“Reality in the Shadows (or) What the Heck’s the Higgs” is meant to help a new audience come to discover a love of science and especially physics, or to welcome to the frontier those who already discovered that love a long time ago.

“Reality in the Shadows (or) What the Heck’s the Higgs” by S. James Gates Jr., Frank Blitzer, and Stephen Jacob Sekula. Available from Amazon.com, Barnes and Noble, and YBK Publishers. $26.95.


In recent years, we have learned that the commonplace materials described by the scientific findings we have so far discovered portray but a tiny piece of a much greater universe–a universe ruled by vast mysteries that appear to shape reality at both its largest and smallest sizes. That universe is now coming to be better understood. You will see how this has happened and how the shadows in the unknown slowly continue to be lit and identified.

Reality in the Shadows is a chronicle of the men and women who cast light on these mysteries of our existence, a look into some of the brilliant ideas that they presented, and a longer look at the new and even greater mysteries of the cosmos that now cry for scientific explanation. It is also an opportunity to become familiar with a now-famous particle– the Higgs Boson–that is both a telling-out of some very old questions and the beginning for hundreds of new and yet-to-be-answered ones.

This book is written for the lay person–someone very interested in this subject, who may not have had a lot of technical preparation. It was prepared to make the material as engagingly easy to read as possible and provides many analogies and explanations.

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