What the Brain’s Function Tells Us About Science and Reality (Putnam Series, Pt. 2)
An old story about mind and matter with modern evidences.
They will understand me alright when they realize they have got to do so.
Sir Arthur Eddington, the scientist best known for confirming Einstein’s General Relativity during the 1919 solar eclipse, wrote this message in 1944 shortly before he passed away.
In the early 20th century, physics, once believed to speak for the objective truth, suddenly became not so objective. The new foundational theories - quantum physics and relativity, both have the observer mysteriously in the formalization. Eddington had devoted himself to developing the “fundamental theory”, in which he argued that the laws of physics are not purely objective features of the universe, but rather a result of our methods of measurement and observation. He famously illustrated the idea with the fisherman analogy. Suppose a fisherman casts a net in the ocean and the fish he gets every time are more than inches long. The fisherman concludes that all fish are longer than two inches, when the reality is that his net with a mesh size of two inches can’t catch fish smaller than that.
Is physics a study of the fish (the objective truth “out there”), or a study of the net (our measurement)? How much can we know about reality? From 1947 to 1962, Peter Putnam spent 15 years struggling to decipher Eddington’s message. He detoured from Eddington’s “Fundamental Theory” and started from the most fundamental question to build up his answer; that fundamental question is how our mind is created.
Today, we will deep dive into his model of human mind and see what it says about our reality.
Reality Is More Fluid than We Thought
From infants to toddlers to children, we have inherited or developed basic heuristics for satisfying our basic drives - hunger, thirst, curiosity, safety etc. We wander away from parents out of curiosity; we put editable looking things into our mouth when hungry; we have simple ways to label people as either good or bad. However, these heuristics tend to over generalize (we call it “naive”), and as we encounter more complex environments, they run into contradictions - for example, our curiosity often puts us in dangerous situations.
One of Putnam’s great insights is, the overarching drive for the development of the human mind, as we mature, is to resolve the latent inconsistency of our own heuristics.
We all feel moments of contradiction, just like we can feel other biological drives. Sometimes, we pause to think, trying to figure out what went wrong and what to do next. Sometimes, we are caught by surprise and we make adjustments. But other times, we feel embarrassed, angry or even desperate, because we think it is a contradiction between our heuristic and reality. “I should have known this!” “S/he is ridiculous!” We told ourselves. But the fact is, submitting to the “reality” or treating something as reality is also a heuristic; we consider it the “reality” simply because we have put so much weight in that particular heuristic. However, history and our own experiences have proved again and again that “reality” can be “wrong”. Of course, I have to quote “wrong” as well because there is no absolute right or wrong - all we can figure out, all the brain cares about, is which set of heuristics provide better internal consistency.
History and stories are full of mistakes and tragedy caused by submitting to “reality”. On the flip side, hopes and breakthroughs almost always come from challenging reality in search of a deeper level of consistency.
Reality Is the Result of Information Processing
But what indeed is a contradiction? Putnam’s other great insight is, contradiction comes from different heuristics pointing to conflicting next “word”.
In Putnam’s definition, a word by the brain is an abstract concept that represents a high level unit of information. It can be something that catches your attention, a thought that comes to your mind or an emission of a motor action. But just like words we say, words by the brain are discrete, and mutually exclusive. This discrete, mutually exclusive nature comes from our biological constraints. One body part can only move in one direction at a time. Within the brain, excited neurons inhibit nearby neurons from being excited; basal ganglia is the “gatekeeper” that makes sure high level actions are ordered sequentially. All these constraints contribute to our sense of linear consciousness, and create a battle between two heuristics to make the next word.
A heuristic defines what the next word should be given some past words as the context. For example, “A, B -> C” is a heuristic. Conflicting heuristics cause new words to be identified, or a word to be split into more fine grained words. For example, if there is another heuristic “A, B -> D”, the conflict between the two may cause the brain to further separate word B into B1 and B2. The first heuristic now becomes “A, B1 -> C” and the second one becomes “A, B2 -> D”, which are consistent.
Even our very basic words are formed through this refining process. Identifying different shapes - circles, squares, etc, for example, comes from the contradiction that tracking different shapes requires different sequences of eyeball movements (The Scanpath Theory). In the process of resolving the contradiction such that we can track more smoothly, the brain builds the neural network for isolating these words (i.e. separating different shapes) through the visual sensory input.
Through contradiction resolution, we constructed the words that define our reality as things and their relationships and movements in space-time. Physics and other science are built on top of things in space-time. However, Putnam argued, the brain’s functional model is more fundamental than things in space-time, so when those theories break down, we should go back to thinking in terms of “words”.
Science Is Self Predicting
Each of us has developed our own set of words and heuristics for making the next words. We build stronger confidence in some of the heuristics because in our history, they have been applied and withstood contradictions many times, and when we look at other people, we see these heuristics resolve their contradictions as well. We call these person-independent heuristics “facts”, which are “objective”.
Person-independent heuristics at the beginning are isolated. As they accumulated, we tried to compress them to fewer more general heuristics by extracting their latent structure. All aspects of human epistemology - science / physics, politics, culture, religion - all attempts to do the same. The only difference is, physics aims to systematize the set of heuristics that apply to everyone, regardless of their political attitude, culture and religion.
With this perspective of physics, Putnam has offered a very simple interpretation of quantum physics (which is actually very similar to QBism):
Don’t think about things in space-time when you think about the wavefunction. If you do this, you will be hallucinating by projecting existing concepts to out-of-distribution data. The wavefunction is simply a heuristic that tells us the possible outcomes of an observation and their probabilities, based on past experiences. By deciding to set up the experiment and observing the system, the brain writes the observation of one of the possible outcomes as the next word, which couldn’t be predicted before doing the observation.
Side note: one interesting property of physics laws (Newton’s law, quantum physics, relativity) is that information stays constant during the evolution of the system. I didn’t have any intuition why but I now realize it is by design - physics is a summary of our past knowledge, so in order for them to be correct, it can’t create new information. Only human decision making can bring new information to reality!
Putnam Quotes
As usually, let’s end this part of the series with some direct quotes from this unknown great thinker:
Causal law [the objective truth] can never be fully known. The more we learn about it, the more we discover our own ignorance, and open up new areas for investigation. Matter itself is a transcendental category. Every new layer of structure in matter, when opened, gives rise to a theory, via which we can isolate a whole new technology. This new technology not only allows us to open new layers of matter, but it also transforms the social order, and even forces a differentiation of the concept of the self--or the design of brains.
Nor can emotionally significant major human issues ever be predicted... The reason for this is that the center of attention is a function of the inconsistencies in our best available self-models, and so can not be predicted by these self-models.
- Some Comments on the Functional Form of the Life Game, Peter Putnam, 1968