CHAPTER XII
Minds and Thoughts
Can Minds Be Mapped onto Each Other?Now TH AT WE have hypothesized the existence of very high-level active
subsystems of the brain (symbols), we may return to the matter of a possible
isomorphism, or partial isomorphism, between two brains. Instead of ask-
ing about an isomorphism on the neural level (which surely does not exist),
or on the macroscopic suborgan level (which surely does exist but does not
tell us very much), we ask about the possibility of an isomorphism between
brains on the symbol level: a correspondence which not only maps symbols
in one brain onto symbols in another brain, but also maps triggering
patterns onto triggering patterns. This means that corresponding symbols
in the two brains are linked in corresponding ways. This would be a true
functional isomorphism-the same type of isomorphism as we spoke of
when trying to characterize what it is that is invariant about all butterflies.
It is clear from the outset that such an isomorphism does not exist
between any pair of human beings. If it did, they would be completely
indistinguishable in their thoughts; but in order for that to be true, they
would have to have completely indistinguishable memories, which would
mean they would have to have led one and the same life. Even identical
twins do not approach, in the remotest degree, this ideal.
How about a single individual? When you look back over things which
you yourself wrote a few years ago, you think "How awful!" and smile with
amusement at the person you once were. What is worse is when you do the
same thing with something you wrote or said five minutes ago. When this
happens, it shows that you do not fully understand the person you were
moments ago. The isomorphism from your brain now to your brain then
is imperfect. What, then, of the isomorphisms to other people, other
species ...?
The opposite side of the coin is shown by the power of the communica-
tion that arises between the unlikeliest partners. Think of the barriers
spanned when you read lines of poetry penned in jail by Fran~ois Villon,
the French poet of the 1400's. Another human being, in another era,
captive in jail, speaking another language ... How can you ever hope to
have a sense of the connotations behind the facade of his words, translated
into English? Yet a wealth of meaning comes through.
Thus, on the one hand, we can drop all hopes of finding exactly
isomorphic software in humans, but on the other, it is clear that some
people think more alike than others do. It would seem an obvious conclu-
Minds and Thoughts^369