11 September 2019

Reductionism can explain neither carrots nor consciousness

Trying to understand a whole as simply a sum of its parts hasn’t worked out well in nutrition or many other fields of science.

I have recently taken up the habit of going to the gym. More new habits have followed, like counting the calories I eat and being hyper-aware of how much protein is in everything.

But since I’m generally skeptical of things, I started to wonder whether all these changes to my diet are actually for the best. After skimming a handful of books on nutrition to get some clarity on the question (noting how many contradictions I was finding even on first glance), I settled on reading Michael Pollan’s 2008 book, In Defense of Food.

Pollan shares my skepticism about whether the various foods that cater to “healthy, active” people are truly a leap forward in nutritional science or just more fads. He approaches the subject by discussing how nutrition science, since the beginning, has been obsessed with viewing food as primarily a collection of nutrients, vitamins, and other too-small-to-be-seen substances.

Food = nutrients?

In 1827, William Prout proposed three “staminal principles” that make up all food. We know these today as protein, fat and carbohydrates (a.k.a. macronutrients). Others soon built on his work, feeling confident the secrets of nutrition had been unlocked. Evidence of how much was left to know quickly appeared. According to Pollen, babies unlucky enough to be fed an early baby formula “failed to thrive” because it lacked numerous nutrients found in breast milk.

As the field progressed, each additional discovery (vitamins! amino acids!) would give nutrition scientists hope they had finally completed the picture and were able to understand what really makes food “healthy”.

So if you’re a nutrition scientist you do the only thing you can do, given the tools at your disposal: Break the thing down into its component parts and study those one by one, even if that means ignoring subtle interactions and contexts and the fact that the whole may well be more than, or maybe just different from, the sum of its parts. This is what we mean by reductionist science.

And so the story goes to the present day, with the creations of food scientists still failing to equal or surpass the health benefits of “real” food. Pollan puts it simply: “We know how to break down a kernel of corn or grain of wheat into its chemical parts, but we have no idea how to put it back together again.”

From a common sense point of view, the approach taken by these scientists can’t be faulted. How do we learn about things? We take them apart, see what’s inside and try to put them back together again. (And maybe make some improvements along the way.)

But reading Pollan’s critique of reductionist science made me curious to look deeper at this approach within other disciplines. It seems that the failure of reductionism to understand nutrition is just one failure among many.

Nothing but a pack of neurons

Physicist David Deutsch has defined reductionism as “the misconception that science must or should always explain things by analysing them into components (and hence that higher-level explanations cannot be fundamental).”

This desire to break down complex phenomena into the smallest possible components and claim the complex phenomena to be nothing but these components can shoulder much of the blame for what philosopher Galen Strawson has called “the silliest claim that has ever been made”. What’s the claim? That consciousness doesn’t exist. Francis Crick gives a rough guide to the sort of reasoning behind this belief (though he doesn’t personally deny the existence of consciousness):

The Astonishing Hypothesis is that “You”, your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules. As Lewis Carroll’s Alice might have phrased it: “You’re nothing but a pack of neurons”.

We know that “a pack of neurons” can’t linger on embarrassing moments from childhood or feel bored during a meeting, and since we’re nothing but that, then consciousness must not exist.

Yeah, that sounds pretty silly to me, too. Later in the same essay Strawson touches on the limitations of science to explain phenomena like consciousness:

Physics may tell us a great deal about the structure of physical reality insofar as it can be logico-mathematically represented, but it doesn’t and can’t tell us anything about the intrinsic nature of reality insofar as its intrinsic nature is more than its structure…

Philosopher Bryan Magee has also written about this same limitation of science:

Physics, for example, reduces the phenomena with which it deals to constant equations concerning energy, light, mass, velocity, temperature, gravity, and the rest. But that is where it leaves us. If we then raise fundamental questions about that ground-floor level of explanation itself, the scientist is at a loss to answer. This is not because of any inadequacy on his part, or on science’s. He and it have done what they can. If one says to the physicist: “Now please tell me what exactly is energy? And what are the foundations of this mathematics you’re using all the time?” it is no discredit to him that he cannot answer. These questions are not his province.

Perhaps it’s just these limitations of scientific explanation that drives the reductionist to claim the non-existence of things that cannot be caught within its grasp.

The Universal Flux

With all that said, the spirit behind reductionism has paid handsome dividends. As Magee wrote right before the passage quoted above, “What [science] does—and this is one of the supreme cultural as well as intellectual achievements of mankind—is reduce everything it can deal with to a certain ground-floor level of explanation.”

But as we attempt to peer ever deeper into the heart of things, it’s unlikely that the ultimate nature of reality can be found by just looking for smaller and smaller components.

David Bohm was a physicist who explored the strange territory of ultimate foundations. In his 1980 book, Wholeness and the Implicate Order, he set forth the concept of implicate and explicate order, a mind-bending account of ultimate reality. Rejecting reductionism, he had this to say:

So one will not be led to suppose that all properties of collections of objects, events, etc., will have to be explainable in terms of some knowable set of ultimate substances. At any stage, further properties of such collections may arise, whose ultimate ground is to be regarded as the unknown totality of the universal flux.

At this stage of our understanding as a species, we’re still ignorant to the full complexities of things, whether it be consciousness or a carrot. Looking carefully at the parts is one way of approaching difficult problems, but better explanations will likely be found by considering them as whole, complex systems.