It has always been the stuff of comic books and sci-fi films, the idea that it might be possible to become invisible.
Recently, however, scientists working in the University of California, Berkeley, have established that they can cover an object with a kind of cloak, a mere 0.00008mm thick, which distorts the reflected light from the concealed object, making it look as if deriving from a flat surface. Up to now, all that has been concealed in this way are objects the size of a few biological cells. In theory, though, the technology involved could be developed to make much larger objects invisible, including, perhaps, human beings.
Why does such a prospect seem so exciting? Perhaps it is because of the power over others which it implies, together with the ability to deceive and manipulate.
Writing nearly 2,500 years ago, the philosopher Plato invited his readers to consider the idea of a magical ring, the so-called Ring of Gyges, which when placed on the finger rendered the wearer invisible.
Would such a power, asked Plato, make a person less inclined to act morally, if he knew that, no matter what injustices he might commit, he would have no need to fear the possibility of being caught and punished?
In other words, do we behave ourselves well toward others merely because we are conscious of their gaze and do not wish to lose face in public, or do we act justly from some higher motive? Are ethics, as someone once argued, something we do when no-one is looking, or are they a product of social constraint?
The conclusion in The Republic, as voiced by Socrates, is that anyone who allowed himself to be aroused by the possibility of using the ring for immoral purposes had already proven that he was a slave to his baser appetites and was, therefore, unworthy, whilst the person who would not succumb to such temptation was someone of great self-control and therefore happy.
It remains, surely, an interesting question to ask of ourselves. If such technology as that developed in California were to become available, how would we use it?
To become invisible presences for good in the world, doing acts of charity without the expectation of earthly reward, or voyeurs and exploiters, able to indulge the darker side of our natures?
I suspect, if we are honest, the latter possibility, if not actually put into practise, would not be entirely free from our minds.