ACHILLES: I see things so much more easily in the “bit-at-a-time” picture.
TORTOISE: Of course you do. The human brain is set up to see that that way. Even in a simple case, like the motion of a flying grapefruit the brain is more satisfied to see the actual motion “a bit at a time” than it is to visualize a parabola “all at once.” But simply coming to recognize that there is an “all-at-once” picture was a great step by the human mind, because it amounted to the recognition that so regularities exist in nature, regularities that guide events in predictable channels.
ACHILLES: I recognize that feeling exists in the “bit-at-a-time” picture. I know this because that is how I feel my own feelings. But does it also exist in the “all-at-once” picture? Are there “feelings” in a motionless book?
TORTOISE: Is there music in a motionless playing-record?
ACHILLES: I am not sure any longer how to answer that question. But I still want to learn if “I” am in the Achilles book, or if the “real Einstein” is in the Einstein book.
TORTOISE: So you may; but for my part, I still want to learn if “you” are anywhere at all. So let us stick to the comfortable “bit-at-a-time” picture, and imagine the internal processes of your brain, Achilles. Imagine the “hot-spot,” that infamous shower of electrochemical activity, as it zigzags its way along the “path of least resistance.” You, Achilles, or what you refer to as “I,” have no control over which path is the one of least resistance.
ACHILLES: I don’t? Is it my subconscious, then? I know I sometimes feel my thoughts “spring up” to me as if motivated by subconscious tendencies.
TORTOISE: Perhaps “subconscious” is a good name for neural structure. It is, after all, your neural structure that, at any moment, determines which path is the one of least resistance. And it is because of that neural structure that the “hot-spot” follows that curlicue path and none other. This swirling electrochemical activity constitutes the mental and emotional life of Achilles.
ACHILLES: A weird and mechanistic song, Mr. T. I bet you could make it sound even stranger. Wax lyric if you can; let the verbs have their fling! Of Brain, Mind, and Man, let’s hear the Tortoise sing!
TORTOISE: Your verse is surely inspired by the gods, my dear companion. The brain of Achilles is like a labyrinth of rooms; each room has many doors leading to other rooms—and many of the rooms are labeled. (Each “room” may be thought of as a complex of a few or a few dozen neurons—perhaps more; and “labeled” rooms are special complexes composed mostly of speech-neurons.) As the “hot spot” tears through this labyrinth, flinging open and slamming shut doors, from time to time it enters a “labeled” room. At that point your throat and mouth contract: you say a word. All the while the neural flash loops relentlessly along its Achillean path, in shapes stranger than the dash of a gnat-hungry swallow; every twist, every turn is foreordained by the neural structure present in your brain, until sensory input messages interfere; then the flash veers away from the path it would have followed. And so it goes—room after room after labeled room is visited. You are speaking.
ACHILLES: I don’t always speak. Sometimes I merely sit and think.
TORTOISE: Granted. The labeled rooms may have their lights turned low—a sign for non-utterance: you don’t speak the words aloud. A “thought” occurs, silently. The hot spot continues—depositing, at door after door, either a drop of oil on the hinge to loosen it, or a drop of water to corrode it. Some doors have such rusty hinges they can’t be opened. Others are so often oiled they nearly open by themselves. Thus traces of the present are deposited for the future: the “I” of now leaves messages and memories for the “I” of a time to come. This neural dance is the dance of the soul; and the sole choreographer of the soul is physical law.
ACHILLES: Normally, I think that I’m in control of what I think; but the way you put it turns it all around backward, so that it sounds like “I” am just what comes out of all this neural structure and natural law. It makes what I consider myself sound at best like a by-product of an organism governed by natural law and, at worst, like an artificial concept produced by my distorted perspective. In other words, you make me feel as if I don’t know who—or what—I am, if anything.
TORTOISE: This is a very important matter to bring up. How can you “know” what you are? First of all, what does it mean to know something, anything, at all?
ACHILLES: Well, I presume that when I know something—or when, should I say, my brain knows something—there is a path that snakes through my brain, running through rooms, many of which are labeled. If I ever think a thought about the subject, my neural flash swishes along that path quite automatically, and if I am conversing, each time it passes through a labeled room, a sound of some type comes out. But of course I don’t need to think about my neural flash for it to do this very competently. It seems as if I function quite well without me!
TORTOISE: Well, it’s true that the “path of least resistance” does take care of itself quite well. But we can equate the result of all this functioning with you, Achilles. You needn’t feel that your self is dispensed with in this analysis.
ACHILLES: But the trouble with this picture is that my “self” is not in control of myself.
TORTOISE: I suppose it depends upon what you mean by “control,” Achilles. Clearly you cannot force your neural flash to deviate from the path of least resistance; but the Achilles of one moment is directly affecting what will become the path of least resistance in the next moment. That should give you some feeling that “you,” whatever you are, have some control over what you will feel and think and do, in the future.
ACHILLES: Well, yes, that is an interesting way to look at it, but it still means that I can’t just think whatever I want to think, but only what was set up for me to think, by an earlier version of me.
TORTOISE: But what is set up in your brain is what you want to think about, to a large degree. But sometimes, admittedly, you can’t make your brain function as you will it to. You forget someone’s name; you can’t concentrate on something important; you become nervous despite your best attempts to control yourself; all of this reflects what you said: that in a sense your “self” is not in control of yourself. Now it is up to you whether or not you wish to identify the Achilles of now with the Achilles of bygone times. If you do choose to identify with your former selves, then you can say that “you”—meaning the you that used to exist—are in control of what you are today; but if you prefer to think of yourself as existing solely in the present, then indeed it is true that what “you” do is under control of natural law and not under control of an independent “soul.”