ACHILLES: Well, to tell the truth, Mr. T, I must confess to a shortcoming in my aesthetic capacities: I doubt that I would know how to visually interpret the printed symbols in front of me in such a way as to give me the same pleasure as I gain from the actual hearing.
TORTOISE: I am sorry indeed to hear that. Why, it could save you so much time! For imagine, instead of wasting a full hour listening to a Beethoven symphony, on waking up some morning you could simply open your eyes and take it all in, hanging there on your wall, in ten seconds or less, and be refreshed and ready for a fine, fulfilling day?
ACHILLES: Oh, you do poor Beethoven an injustice, Mr. T, a sorry injustice.
TORTOISE: Why, not at all. Beethoven is my second favorite composer. I have spent many long minutes gazing at his beautiful works, both in score and on playing record. The sculpted forms in some of his playing records are so exquisite, you have no idea.
ACHILLES: I must admit, you have floored me. That is an odd way, to put it mildly, to enjoy music. But I suppose you are an odd character, and this idiosyncrasy makes as much sense, given what I know of you any of the rest.
TORTOISE: A condescending view. How would you like it, if some friend “revealed” to you that you’d never correctly understood a Leonardo painting—in reality, it should be listened to, not looked at, and is sixty-two minutes long, in eight movements, and contains long passages with nothing but the loud ringing of many different-sized bells?
ACHILLES: That is an odd way to think of paintings. But…
TORTOISE: Did I ever tell you about my friend the alligator, who enjoys music while lying on his back in the sun?
ACHILLES: Not that I recall.
TORTOISE: He has the advantage of having no shell covering his belly. So whenever he wants to “hear” a lovely piece, he picks out the appropriate disk and slaps it sharply for an instant against his stomach. The ecstasy of absorbing so many luscious patterns all a once, he tells me, is indescribable. So just think—his experience is, as novel to me as mine is to you!
ACHILLES: But how can he tell the difference between one record and another?
TORTOISE: To him, slapping Bach and Beethoven against his belly are as different as to you slapping a waffle iron and a velvet pad against your bare back would be!
ACHILLES: In so turning the tables on me, Mr. T, you have shown me one thing—your point of view must be just as valid as mine—and if I did not admit it, I should be an auditory chauvinist pig.
TORTOISE: Well put—admirably put! Now that we have gone over our relative points of view, I will have to confess to being familiar with your way of listening to playing records, rather than looking at them, odd though it does seem to me. The comparison between the two types of experience was what inspired me to exploit this example as an analogy to what I wish to present to you now, Achilles.
ACHILLES: More of your usual trickery, I see. Well, go on with it—I’m all eyes.
TORTOISE: All right. Let’s suppose that I came to you one morning with a very big book. You’d say, “Hullo, Mr. Tortoise—what’s in that big book you’re carrying with you?” (if I’m not mistaken); and I’d reply “It’s a schematic description of Albert Einstein’s brain, down to the cellular level, made by some painstaking and slightly crazy neurologist after Einstein died. You know he bequeathed his brain to science, don’t you?” And you’d say, “What in the world are you talking about, ‘a schematic description of Albert Einstein’s brain, down to the cellular level’?” would you not?
ACHILLES: I certainly would! The notion sounds preposterous. I suppose you’d go on roughly as follows: “Probably you’re aware, Achilles, that a brain—any brain—is composed of neurons, or nerve cells, linked together by fibers called ‘axons’ to form a highly interconnected network.” I’d say interestedly, “Go on.” So you would.
TORTOISE: Bravo! You’re doing very well! You took the words right out of my mouth! So I would indeed go on, as you suggested. I’d continue, “The details are beside the point here, but a little knowledge is essential. These neurons are known to fire, which means that a minuscule electric current (regulated by the resistance of the axon) passes down an axon into an adjoining neuron, where it may join other signals in a combined effort to ‘trigger’ this neighbor-neuron to fire in turn. The neighbor, however, will cooperate only if the sum of the incoming currents has reached a threshold value (which is determined by its internal structure); otherwise it will refuse to fire at all.” At this point, you might say, “Hmm.”
ACHILLES: So how would you go on, Mr. T?
TORTOISE: A good question. I suppose I might say something like this: “The foregoing is a peanut-sized summary of the goings-on in a brain, but I suppose it’s sufficient background for an explanation of what this heavy book is that I’m carrying about with me today.” If I know you at all, you’d say, “Oh, I’m eager to hear about it, but perhaps I should be warier, lest it contain one of your infamous schemes, whereby you lure poor little unsuspecting me into one of your inescapable absurdities.” But I’d reassure you that no such prospect was in store, and thus reassured, you’d urge me to divulge the contents of the book, about which you, having taken a peek in it, might say, “It just looks like a lot of numbers and letters and little abbreviations and things!” And I’d say, “What did you expect? Little pictures of stars and galaxies and atoms, whirling about with formula such as ‘E = mc2’ scattered hither and thither?”
ACHILLES: At that swipe, I might take offense. I’d say indignantly, “Certainly not.”
TORTOISE: Of course you would—rightly so. And then you’d say, “Well, what are all those numbers and things? What do they stand for?”
ACHILLES: Let me go on. I can anticipate, I believe, just how you’d reply: “Each page of this book—and there are around a hundred billion numbered pages in it—corresponds to one neuron and contains numbers recording such aspects relevant to that neuron as: which other neurons its axons lead to, what its threshold current is for firing, and so on. However, I forgot to tell you certain further important facts about the functioning of brains in general—in particular what happens, or is believed to happen (from all we know from neurological research), when thoughts occur in the brain, and especially conscious thoughts.” I might object with some vaguely worded complaint about thoughts occurring in the mind, not the brain, but you’d hastily dismiss that remark and say, “We can talk about that some other time—say, for example, if we meet by chance in the Jardin du Luxembourg someday. But for now my goal is to explain the contents of this book to you.” I’d be placated, I suppose, as I usually am, so you’d press on with a comment in this vein: “A thought occurs (in the mind or the brain, whichever you prefer—for now!) when a series of connected neurons fire in succession—mind you, it may not be a long string of individual neurons firing like chain of dominoes falling down one after another—it may be more like several neurons at a time tending to trigger another few, and so forth. More likely than not, some stray neural chains will get started along the side of the mainstream but soon will peter out, as threshold currents are not attained. Thus, one will have, in sum, a broad or narrow squad of firing neurons, transmitting their energy to others in turn, thus forming a dynamic chain that meanders within the brain—its course determined by the various resistances in the axons that are encountered along the way. It would not be out of place to say that ‘the path of least resistance is followed,’ if you follow me.” At this point, I’d be sure to comment, “You’ve surely said a mouthful—let me have a moment to digest it.” After mulling over this food for thought you’d so far provided me with, and asking you a few clarifying questions on it, I’d be satisfied that I’d gotten the general picture. Of course you’d probably tell me that if I wanted more information on the subject, I could easily go look it up in almost any popular book about the brain. So then you’d say, “Let me wind up this description of neural activity by briefly describing what accounts for memory, at least as well as has been so far established. Think of the ‘flashing spot of activity’ careening around within the brain (‘where all the action is,’ so to speak) as a boat traveling across the surface of a pond, such as those toy sailboats that children sometimes bring to the octagonal ponds in the Jardin du Luxembourg, the site of our hypothetical mind-brain encounter; every boat leaves a disturbance behind it, its wake, as it travels through its medium. The ‘hot spot’ within the brain, just like the boat, leaves its own kind of disturbance, or wake, behind: the neurons that just fired as the signal came through continue to undergo some kind of internal activity—perhaps chemical in nature—for a few seconds. A permanent change in the neuron is thereby effected. The change is reflected in some of the numbers we have already spoken of, such as the threshold value for firing, the axon resistances, and so forth. The exact way in which those numbers are modified is, of course, dependent on certain aspects of the internal structure in question—and these aspects themselves are susceptible to numerical encoding.” I might well chime in at this point, I imagine, saying “Hence it would be of utmost importance to record those numbers for every neuron, as well as the already-mentioned resistances and thresholds.” You would no doubt reply, “An astute remark, Achilles; I had not anticipated you’d see that necessity so quickly. And we might do well to give those numbers a name too: the ‘structure-altering numbers’ seems adequate to me.” To conclude this exchange, I might make the following sort of remark: “The structure-altering numbers are quite remarkable in that they not only describe how other numbers on the page are to change, but also how they themselves are to change, next time the neural flash comes passing through!”