Hierarchy of the Sciences?

Jerry Lettvin was one of several treasured mentors in my life. He was an MD and an electrical engineer, holding positions in biology and electrical engineering at MIT.

I was a student in a most unique program he ran at MIT called “Concourse.” We did the usual classes, but we were in a smaller group, and we had additional seminars with some of the great minds of the time in the 1970s.

One day Jerry (he invited us to call him Jerry) gave us a perspective on the “hierarchy of the sciences.” Apparently, this was written formally by French mathematician and philosopher of science Auguste Comte in the 1800s.

Comte arranged a hierarchy of the sciences with Mathematics at the base. The hierarchy ascended in order: Physics, Chemistry, Biology, Psychology, Sociology. Underneath all of this was Logic.

Comte argued that the lower sciences in the hierarchy are more simple and more general. They are also more likely to achieve “positive results,” meaning accurate predictions. Comte believed that, over time, the higher-level sciences would develop and grow to become better at making predictions.

He also argued that progress in higher sciences in the hierarchy depends on progress in the levels below.

Jerry presented this as fact and we went on to other topics. But toward the end of the year he revisited this topic in a new talk. He included Engineering in the higher reaches of the hierarchy, dependent on Mathematics, Physics, and Chemistry.

But then he turned this upside down. He argued that Engineering gives us models of the world that actually become the basis of new ideas in all of the other sciences. He therefore declared that Engineering is actually the most fundamental of all sciences.

I told this to some of the other Concourse professors and they insisted I must have misunderstood. They said that would go against everything that Jerry believes.

I followed up with Jerry and he just smiled and assured me that I had understood perfectly. Even though he had said just the opposite in his earlier lecture? He smiled and said yes.

I was majoring in Physics, which included a degree in Mathematics. So I was appalled at the idea that the lowly field of Engineering could be considered more fundamental. But I realized that in an important way he was correct. And that seemingly contradictory concepts can both be true.

Jerry gave some examples. One was how the engineering of a camera gave biologists the understanding of some aspects of how the eye works. In ancient times, Plato believed that the eye emitted rays. Aristotle believed light came into the eye, but had no theory beyond that.

Second century physician Galen learned eye anatomy from Rufus of Ephesus, who actually dissected eyes. But most theories thought vision happened in the lens. It wasn’t until 1604 that the astronomer and mathematician Kepler correctly compared the eye to a “camera obscura.” With the retina being the screen that received the image.

Physics Nobel laureate Richard Feynman said, “What I cannot create, I do not understand.” Feynman worked in the highest levels of theoretical quantum physics. But he never lost his curiosity about building actual devices. He proposed building devices at the atomic scale, which helped inspire the world of nanotechnology; my own career for many years.

And he also suggested the possibility of building a quantum computer – today a multi-billion-dollar quest to harness the counterintuitive physics of the quantum world to build a computer that tries many solutions all at once.

I do believe that Jerry was correct. We think we understand the world from the bottom up. But, in fact, we only really understand the world when we build models. Models that may come from the top down in the form of engineering design.

Another example: Theoretical thermodynamics gave us more efficient engines. But this started with an engineering model of an idealized engine called the Carnot cycle.

I will add that engineering has another symbiotic relationship to the sciences: Engineering develops new tools and instruments to expand science. Everything from the Large Hadron Collider to the James Webb Telescope!