Hi everybody,

This essay is about a computer language called Lisp, and how I believe that it can play a key role in our understanding of the mind-brain connection. To understand the evidence for some claims about Lisp made in this essay, one must read the brilliant essay "The Roots of Lisp" by Paul Graham. This article can be found at:
www.paulgraham.com/rootsoflisp.html

If you don't want to read "Roots of Lisp" right now, you can take another approach: simply note my claims as provisional hypotheses and see if the argument holds together given these hypotheses.

Thanks for reading! This idea is near and dear to my heart, and I feel blessed to be able to share it here with you. Alright, enough metadata, here we go!

MY CENTRAL CLAIM
Lisp is the key to understanding the most fundamental question of human existence: the mind-brain connection.

OUTLINE ARGUMENT FOR THIS CLAIM
0. The brain is essentially a computer.
1. Therefore, to understand how the mind relates to the brain, we must have a computational model of the mind to examine and play with.
2. This "brain-mind" model must have the key ability of the mind: the ability to freely convert between its own language and the interpretation of that language.
3. For us to be able to analyze our "brain-mind" model, it must be simple enough for the human mind to comprehend.
4. Lisp is the first example of a simple, human-comprehensible model of self-interpreting computation.
5. Therefore, Lisp, or something very much like it, is the key to understanding the brain-mind connection.

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ROUGH-DRAFT ESSAY EXPANDING ON THE OUTLINE:

Lisp is a simple collection of symbols obeying a small set of simple
rules, but the system created by defining these symbols and rules has
two amazing properties:

1. Self-interpretation: using only the symbols and rules of Lisp, you
can create a structure called the eval function that is able to
"interpret the meaning" of code written in Lisp.
2. Human comprehensibility: the eval function, while not trivial to
understand, is surprisingly simple. It can be written down in a couple
dozen lines of Lisp code. This means it is possible for humans to
understand what it is doing.

Now, what is the most amazing property of human beings? Well, there
are many: complex social structures, the ability to form complex ideas
about the world and turn them into actions, the ability of our ideas
to build upon themselves to make more complex ideas, etc. But these
are all enabled by one root "evolutionary technology": a language that
is "self-aware".

Let me explain what I mean more precisely. We have the ability to
store our language "code" in our minds, and we are free at any time to
interpret, or "evaluate", this code to convert it into ideas. It is
this ability that enables us to encode useful concepts into language
and use them to build complex ideas out of simple ones. For example,
think about your ability to talk about evolutionary theory. The term
"evolutionary theory" is a code that you can "evaluate" to summon a
vast complex interconnecting network of ideas about evolutionary
theory that exists in your mind. You have the amazing ability to
magically "summon" that entire network of ideas simply by saying the
words "evolutionary theory" to yourself. And this is what makes it
possible for you to build even more complex ideas based off of
evolutionary theory, like "evolutionary theory says that human beings'
genetic structure will change slowly, but our memes can change much
faster.".

If you didn't have the simple term "evolutionary theory" - if you only
had the huge network of ideas - then you would have to "load" the
whole network every time you wanted to work with it, and that would be
impossibly complex for your brain to do. The brain can only build off
of complex ideas by "encapsulating" them into simple language codes
(which can be "interpreted" as needed) and then working with the
language codes to build more complex ideas. In short: our
SELF-INTERPRETING language is the key to our abilities to form complex
ideas.

[Note that in the last sentence, I am using exactly the capability
that is described in the preceding paragraph. I am taking my own
discussion and "encapsulating" it into a simple code -
"self-interpreting language" - which you can use to recall the ideas
discussed in this paragraph! And in just a moment, I will be using
this "encapsulated idea" to build an even more complex idea about how
human thought works! How could you possibly comprehend my idea - how
could I possibly comprehend my idea - if we did not have this amazing
capacity to encapsulate ideas in language, and freely interconvert
from the language to the ideas it represents?]

Now, what is the central obstacle to human beings understanding the
relationship between the brain and the mind? Well, we don't really
understand very well how our brains turn perceptions into thoughts,
thoughts into other thoughts, and thoughts into actions. We know it
has something to do with neurons firing, but we don't have a HUMAN
COMPREHENSIBLE MODEL of how all that neuron-firing turns into the
thoughts we have in our minds. For this model to be effective, it is
strictly necessary that it have the key property of
self-interpretation: the ability to freely convert from its "code"
into the computational "ideas" which the code represents when
evaluated. [Note that I am equating "ideas" with "computations" here;
ideas must be computations because the brain is a neural computer.]

Here is my argument in summary:
0. Understanding how the mind relates to the brain is one of the most
fundamental problems of human existence.
1. To understand how the mind relates to the brain, we must have a
"computational" model of the mind to examine and play with.
2. This "brain-mind" model must have the key ability of the mind: the
ability to freely convert between its own language and the
interpretation of that language.
3. For us to be able to analyze our "brain-mind" model, it must be
simple enough for the human mind to comprehend.
4. Lisp is an example of a simple, human-comprehensible model of
self-interpreting computation.
5. Therefore, to understand the brain-mind connection, we must
understand Lisp or something very much like it.

This is why Lisp is one of the most important achievements in the
history of human thought.