Now as for the second part of the Cassanderish suggestion, the reader might suppose that after each successive partitioning of the brain, synchronization of the parts would have been consistently disregarded, so that eventually it would have been thought not to matter when each individual neuron was to be fired in relation to the firings of the other neurons just as earlier the condition had been disregarded when there were only two hemispheres to be fired. But somehow, perhaps because disregarding the timing and order of individual neuron firings would have reduced the art of programming to absurdity, the condition of order and timing had crept back, but without the Cassanderish reflectiveness. “Right” temporal order of firings is now merely assumed as somehow essential to bringing about a given experience by all those men standing before their baths and waiting for each properly programmed impulse to come to its neuron.
But now, ten centuries after the great project’s birth, the world of these smug billions was about to explode. Two thinkers were responsible.
One of these, named Spoilar, had noticed one day that the neuron in his charge was getting a bit the worse for wear. Like any other man with a neuron in that state, he merely obtained another fresh one just like it and so replaced the particular one that had gotten worn-tossing the old one away. Thus he, like all the others, had violated the Cassanderish condition of “neural identity”—a condition never taken very seriously even by Cassanders. It was realized that in the case of an ordinary brain the cellular metabolism was always replacing all the particular matter of any neuron with other particular matter, forming precisely the same kind of neuron. What this man had done was really no more than a speeding up of this process. Besides, what if, as some Cassanders had implausibly argued, replacing one neuron by another just like it somehow resulted, when it was eventually done to all the neurons, in a new identity for the experiencer? There still would be an experiencer having the same experience every time the same patterns of firings were realized (and what it would mean to say he was a different experiencer was not clear at all, even to the Cassanders). So any shift in neural identity did not seem destructive of the fact of an experience coming about.
This fellow Spoilar, after he had replaced the neuron, resumed his waiting to watch his own neuron fire as part of an experience scheduled several hours later. Suddenly he heard a great crash and a great curse. Some fool had fallen against another man’s bath, and it had broken totally on the floor when it fell. Well, this man whose bath had fallen would just have to miss out on any experiences his neuron was to have been part of until the bath and neuron could be replaced. And Spoilar knew that the poor man had had one coming up soon.
The fellow whose bath had just broken walked up to Spoilar. He said “Look, I’ve done favors for you. I’m going to have to miss the impulse coming up in five minutes—that experience will have to manage with one less neuron firing. But maybe you’d let me man yours coming up later. I just hate to miss all the thrills coming up today!”
Spoilar thought about the man’s plea. Suddenly, a strange thought hit him. “Wasn’t the neuron you manned the same sort as mine?”
“Yes.”
“Well, look. I’ve just replaced my neuron with another like it, as we all do occasionally. Why don’t we take my entire bath over to the old position of yours? Then won’t it still be the same experience brought about in five minutes that it would have been with the old neuron if we fire this then, since this one is just like the old one? Surely the bath’s identity means nothing. Anyway, then we can bring the bath back here and I can use the neuron for the experience it is scheduled to be used for later on. Wait a minute! We both believe the condition of topology is baloney. So why need we move the bath at all? Leave it here; fire it for yours; and then I’ll fire it for mine. Both experiences must still come about. Wait a minute again! Then all we need do is fire this one neuron here in place of all the firings of all neurons just like it! Then there need be only one neuron of each type firing again and again and again to bring about all these experiences! But how would the neurons know even that they were repeating an impulse when they fired again and again? How would they know the relative order of their firings? Then we could have one neuron of each sort firing once and that would provide the physical realization of all patterns of impulses (a conclusion that would have been arrived at merely by consistently disregarding the necessity of synchronization in the progress from parted hemispheres to parted neurons). And couldn’t these neurons simply be any of those naturally firing in any head? So what are we all doing here?”
Then an even more desperate thought hit him, which he expressed thus: “But if all possible neural experience will be brought about simply in the firing once of one of each type of neuron, how can any experiencer believe that he is connected to anything more than this bare minimum of physical reality through the fact of his having any of his experiences? And so all this talk of heads and neurons in them, which is supposedly based on the true discovery of physical realities, is undermined entirely. There may be a true system of physical reality, but if it involves all this physiology we have been hoodwinked into believing, it provides so cheaply for so much experience that we can never know what is an actual experience of it, the physical reality. And so belief in such a system undermines itself. That is, unless it’s tempered with Cassanderish principles.”
The other thinker, coincidentally also named Spoilar, came to the same conclusion somewhat differently. He enjoyed stringing neurons. Once he got his own neuron, the one he was responsible for, in the middle of a long chain of like neurons and then recalled he was supposed to have it hooked up to the cartridge for a firing. Not wanting to destroy the chain, he simply hooked the two end neurons of the chain to the two poles of the impulse cartridge and adjusted the timing of the cartridge so that the impulse, traveling now through this whole chain, would reach his neuron at just the right time. Then he noticed that here a neuron, unlike one in usual experience, was quite comfortably participating in two patterns of firings at once—the chain’s, which happened to have proximity and causal connection, and the programmed experience for which it had fired. After this Spoilar went about ridiculing “the condition of neural context.” He’d say, “Boy, I could hook my neuron up with all those in your head, and if I could get it to fire just at the right time, I could get it into one of these programmed experiences as fine as if it were in my bath, on my cartridge.”
Well, one day there was trouble. Some men who had not been allowed to join the project had come at night and so tampered with the baths that many of the neurons in Spoilar’s vicinity had simply died. Standing before his own dead neuron, staring at the vast misery around him, he thought about how the day’s first experience must turn out for the experiencer when so many neuron firings were to be missing from their physical realization. But as he looked about he suddenly took note of something else. Nearly everyone was stooping to inspect some damaged equipment just under his bath. Suddenly it seemed significant to Spoilar that next to every bath there was a head, each with its own billions of neurons of all sorts, with perhaps millions of each sort firing at any given moment. Proximity didn’t matter. But then at any given moment of a particular pattern’s being fired through the baths all the requisite activity was already going on anyway in the heads of the operators—in even one of those heads, where a loose sort of proximity condition was fulfilled too! Each head was bath and cartridge enough for any spread-brain’s realization: “But,” thought Spoilar, “the same kind of physical realization must exist for every experience of every brain—since all brains are spreadable. And that includes mine. But then all my beliefs are based on thoughts and experiences that might exist only as some such floating cloud. They are all suspect—including those that had convinced me of all this physiology in the first place. Unless Cassander is right, to some extent, then physiology reduces to absurdity. It undermines itself.”