Lewis Carroll had a gift for framing the thorniest issues in the simplest terms. For example in this passage from Alice in Wonderland:
When I use a word," Humpty Dumpty said, in a rather scornful tone, "it means just what I choose it to mean, neither more nor less."
"The question is," said Alice, "whether you can make words mean so many different things."
"The question is," said Humpty Dumpty, ``which is to be master — that's all."
In three sentences he has summed up as neatly as possible the difference between the way mathematicians view words and the way philosophers view words.
My favorite of Carroll's works is a long poem called The Hunting of the Snark—an "agony in eight fits", as Carroll subtitled it. Like all of Carroll's things it is full of silly digressions, but the general theme is that a group of rather extraordinary people go out in quest of something called a "snark", dreading all the while that the snark will turn out to be a "boojum".
Part of the joy of the poem, as with Alice, is the way that deep philosophical issues appear disguised in a mask of absurdity. I like the following passage so much that I used it as the preface to my dissertation:
He had bought a large map representing the sea,
Without the least vestige of land:
And the crew were much pleased when they found it to be
A map they could all understand.
"What's the good of Mercator's North Poles and Equators,
Tropics, Zones, and Meridian Lines?"
So the Bellman would cry: and the crew would reply
"They are merely conventional signs!
"Other maps are such shapes, with their islands and capes!
But we've got our brave Captain to thank
(So the crew would protest) "that he's bought us the best—
A perfect and absolute blank!"
My dissertation dealt (in part) with representations of absolute Euclidean space in the brain. The literature referred to such a representation as a "cognitive map", but it seemed to me that if a representation of abstract space is a map, then it's a map with nothing in it. More to the point, the passage forces one to think about exactly what it means for something to be a map.
One of the remarkable aspects of the poem is that everybody reads it as an allegory, but everybody reads it as a different allegory. What is a snark supposed to be? Or a boojum? If you look around, you can find dozens of hypotheses about what Carroll had in mind. He never explained it himself, and everything in the poem is enigmatic. At one point he (or rather, the Captain) says:
"Come, listen, my men, while I tell you again
The five unmistakable marks
By which you may know, wheresoever you go,
The warranted genuine Snarks. "
But what follows is nonsense.
I am going to give you my own hypothesis. I think that by a "snark" Carroll meant a scientific discovery, and by a "boojum" he meant a scientific discovery that turns out to be spurious, such as cold fusion. Every scientist dreams of finding a snark; every scientist dreads that the snark will turn out to be a boojum. A snark is a wonderful thing:
"He remarked to me then," said that mildest of men,
"'If your Snark be a Snark, that is right:
Fetch it home by all means—you may serve it with greens,
And it's handy for striking a light. "
And any method of finding one is okay as long as it works:
"The rest of my speech" (he explained to his men)
"You shall hear when I've leisure to speak it.
But the Snark is at hand, let me tell you again!
'Tis your glorious duty to seek it!
"To seek it with thimbles, to seek it with care;
To pursue it with forks and hope;
To threaten its life with a railway-share;
To charm it with smiles and soap!
"For the Snark's a peculiar creature, that won't
Be caught in a commonplace way.
Do all that you know, and try all that you don't:
Not a chance must be wasted to-day! "
But the penalty for error is dreadful:
"'But oh, beamish nephew, beware of the day,
If your Snark be a Boojum! For then
You will softly and suddenly vanish away,
And never be met with again!'
Perhaps it is incumbent on me to defend my hypothesis in detail, by pointing out all the things in the poem that accord with it. But I shall refrain from doing so. I have always hated literary criticism. It seems to me that it has the same result as anatomy: if the thing being examined is not dead, the method of examining it will soon make it so. Therefore I leave it to you to read the poem yourself and decide whether my hypothesis makes sense.
Meanwhile I will continue to do science, and hope to avoid the fate of the Baker:
"It's a Snark!" was the sound that first came to their ears,
And seemed almost too good to be true.
Then followed a torrent of laughter and cheers:
Then the ominous words "It's a Boo—"
Then, silence. Some fancied they heard in the air
A weary and wandering sigh
That sounded like "-jum!" but the others declare
It was only a breeze that went by.
They hunted till darkness came on, but they found
Not a button, or feather, or mark,
By which they could tell that they stood on the ground
Where the Baker had met with the Snark.
In the midst of the word he was trying to say,
In the midst of his laughter and glee,
He had softly and suddenly vanished away—
For the Snark was a Boojum, you see.