kind of goal we will be striving for in a chunked description, then it is easy
to see what kinds of troubles we will run up against.
Suppose you wanted to enumerate all possible voyages that could be
taken in an ASU; there are infinitely many. How do you determine which
ones are plausible, though? Well, what does'''plausible'' mean? We will have
precisely this kind of difficulty in trying to establish what a "possible
pathway" from symbol to symbol in a brain is. We can imagine an upside-
down dog flying through the air with a cigar in its mouth-or a collision
between two giant fried eggs on a freeway-or any number of other
ridiculous images. The number of far-fetched pathways which can be
followed in our brains is without bound, just as is the number of insane
itineraries that could be planned on an ASU. But just what constitutes a
"sane" itinerary, given an ASU? And just what constitutes a "reasonable"
thought, given a brain state? The brain state itself does not forbid any
pathway, because for any pathway there are always circumstances which
could force the following of that pathway. The physical status of a brain, if
read correctly, gives information telling not which pathways could be
followed, but rather how much resistance would be offered along the way.
Now in an ASU, there are many trips which could be taken along tWo
or more reasonable alternative routes. For example, the trip from San
Francisco to New York could go along either a northern route or a south-
ern route. Each of them is quite reasonable, but people tend to take them
under different circumstances. Looking at a map at a given moment in time
does not tell you anything about which route will be preferable at some
remote time in the future-that depends on the external circumstances
under which the trip is to be taken. Likewise, the "reading" of a brain state
will reveal that several reasonable alternative pathways are often available,
connecting a given set of symbols. However, the trip among these symbols
need not be imminent; it may be simply one of billions of "potential" trips,
all of which figure in the readout of the brain state. From this follows an
important conclusion: there is no information in the brain state itself which
tells which route will be chosen. The external circumstances will playa
large determining role in choosing the route.
What does this imply? It implies that thoughts which clash totally may
be produced by a single brain, depending on the circumstances. And any
high-level readout of the brain state which is worth its salt must contain all
such conflicting versions. Actually this is quite obvious-that we all are
bundles of contradictions, and we manage to hang together by bringing out
only one side of ourselves at a given time. The selection cannot be pre-
dicted in advance, because the conditions which will force the selection are
not known in advance. What the brain state can provide, if properly read, is
a conditional description of the selection of routes.
Consider, for instance, the Crab's plight, described in the Prelude. He
can react in various ways to the playing of a piece of music. Sometimes he
will be nearly immune to it, because he knows it so well. Other times, he will
be quite excited by it, but this reaction requires the right kind of triggering
from the outside-for instance, the presence of an enthusiastic listener, toMinds and Thoughts 383