Subject:  Thought Experiments – Ring of Gyges

Event:  Birthday of Austrian physicist Ernst Mach

Imagine being a scientist so accomplished that they named the speed of sound after you; furthermore, imagine being so accomplished that Albert Einstein credited you with inspiring his Theory of Relativity.

Ernst Mach, 1905 (Wikipedia Commons)

The scientist imagined above is not a figment of your imagination; instead, he was a real person, the physicist Ernst Mach, who was born on this day in 1838 in Austria.  More than just a scientist though, Mach was also accomplished in the fields of philosophy and psychology.

We often picture accomplished scientists doing experiments in their laboratories, but what we don’t often contemplate is the level of both curiosity and imagination that precede physical experiments.  It is in this area that Ernst Mach was also accomplished, recognized as a pioneer in Gedankenexperiment, the term that originated in Germany and is known today in English as “thought experiment.”

In an essay he wrote in 1897 “On Thought Experiments,” Mach discussed how innate human curiosity is the spark that ignites the imagination, the mind’s laboratory, to visualize ideas long before the become physical facts:

Our own ideas are more easily and readily at our disposal than physical facts. We experiment with thought, so as to say, at little expense. This it shouldn’t surprise us that, oftentime, the thought experiment precedes the physical experiment and prepares the way for it. (1) 

Of course, long before the terms “science” and “thought experiment” were coined, philosophers were employing their imaginations to conduct experiments of the mind.  For example, in Plato’s Allegory of the Cave, Socrates paints an imagined scenario of men living their entire lives chained in a dark cave, seeing shadows rather than reality.  He then imagines what might happen if one of these men were loosed from his chains, freed to see the real world outside the cave.  Through this exercise of imagination, Plato provides us with insight into how philosophy can equip us with a broader view of reality while at the same time warning us of our blind spots and our human tendency to confuse perception with reality.

Another ancient thought experiment from Plato’s Republic, presents a story about human nature that addresses the following questions:  Is it true as the famous quotation by Lord Action proclaims that “Power tends to corrupt and absolute power corrupts absolutely”?  And does true justice exist in the world, or is it just a facade motivated by self-interest?

In the story, a seemingly humble shepherd name Gyges finds a ring that suddenly great powers:

According to the tradition, Gyges was a shepherd in the service of the king of Lydia; there was a great storm, and an earthquake made an opening in the earth at the place where he was feeding his flock. Amazed at the sight, he descended into the opening, where, among other marvels, he beheld a hollow brazen horse, having doors, at which he stooping and looking in saw a dead body of stature, as appeared to him, more than human, and having nothing on but a gold ring; this he took from the finger of the dead and reascended. Now the shepherds met together, according to custom, that they might send their monthly report about the flocks to the king; into their assembly he came having the ring on his finger, and as he was sitting among them he chanced to turn the collet of the ring inside his hand, when instantly he became invisible to the rest of the company and they began to speak of him as if he were no longer present. He was astonished at this, and again touching the ring he turned the collet outwards and reappeared; he made several trials of the ring, and always with the same result—when he turned the collet inwards he became invisible, when outwards he reappeared. Whereupon he contrived to be chosen one of the messengers who were sent to the court; whereas soon as he arrived he seduced the queen, and with her help conspired against the king and slew him, and took the kingdom. 

After telling the story of the Ring of Gyges, the narrator asks the reader to join him in a thought experiment:

Suppose now that there were two such magic rings, and the just put on one of them and the unjust the other; no man can be imagined to be of such an iron nature that he would stand fast in justice. No man would keep his hands off what was not his own when he could safely take what he liked out of the market, or go into houses and lie with any one at his pleasure, or kill or release from prison whom he would, and in all respects be like a God among men. Then the actions of the just would be as the actions of the unjust; they would both come at last to the same point. And this we may truly affirm to be a great proof that a man is just, not willingly or because he thinks that justice is any good to him individually, but of necessity, for wherever any one thinks that he can safely be unjust, there he is unjust. For all men believe in their hearts that injustice is far more profitable to the individual than justice, and he who argues as I have been supposing, will say that they are right. If you could imagine any one obtaining this power of becoming invisible, and never doing any wrong or touching what was another’s, he would be thought by the lookers-on to be a most wretched idiot, although they would praise him to one another’s faces, and keep up appearances with one another from a fear that they too might suffer injustice. 

The thought experiment attempts to illustrate the paradox of justice — that justice and injustice, instead of being opposites, are really the same thing.  Justice is never authentic; instead, it is merely an act, motivated by the fear of being exposed for who we really are: people who would act unjustly if we, like Gyges, could get away with it.

Recall, Retrieve, Recite, Ruminate, Reflect, Reason:  What is the Ring of Gyges thought experiment, and how does it challenge our thinking about justice?

Challenge – Imagination Lab:  Research some other famous thought experiments.  Pick one that captures your imagination.  Explain the thought experiment, and explain why you find it interesting.


February 18, 1884:  Mark Twain’s The Adventures of Huckleberry Finn was published. Unlike other American novels of the time, which were imitations of European literature, Huckleberry Finn was a truly American book, the first to be written in the American vernacular.  Twain’s revolutionary move was to give the narration of his book to the uneducated, unwashed Huck, who speaks in dialect and introduces himself in the novel’s famous first sentence:

You don’t know about me without you have read a book by the name of The Adventures of Tom Sawyer; but that ain’t no matter. That book was made by Mr. Mark Twain, and he told the truth, mainly. There was things which he stretched, but mainly he told the truth. That is nothing. I never seen anybody but lied one time or another . . . .    


1-Thought Experiment: How Einstein Solved Difficult Problems. FS Blog.

2-“Plato: Ethic – The Ring of Gyges.” Great Philosophers. Oregon State University.