"When we try to pick out anything by itself, we find it hitched to everything else in the universe." -- John Muir
When Descartes partitioned the world into the res extensa (material objects) and the res cogitans (mind), he treated the two domains quite differently. In chapter VI of Meditations and Principles (1644), he writes:
"... there is a vast difference between the mind and body, in respect that body, from its nature, is always divisible, and that mind is entirely indivisible."
The body he viewed as a machine, which could be understood by the interactions of its constituent parts. Hence, the dissection of material objects, in general, into their components -- that is, reductionism -- was seen as a viable approach to understanding the whole.
Many quarters of science have benefitted from reductionist investigations. Modern medicine owes much of its efficacy to understanding the functions of the various organs -- the heart, lungs, kidneys, and so on -- and to their contributions to the physiology of the whole. Likewise the standard model of particle physics has resulted from physics' relentless persistence in probing the structure of matter, all the way down to its tiniest ingredients -- protons, electrons, and neutrons -- as well as the quarks that comprise these basic constituents and the forces that glue them together. Gilding the lily of the standard model was the recent discovery of the long-elusive Higgs boson, colorfully (but misleadingly) dubbed the "God particle."
Biology too has made great leaps through reductionism. By laser-like focus on the genetic molecule, science unraveled the structure of DNA in 1953, paving the way for the decoding of complete genomes a half-century later. In particular, the massive Human Genome Project (HGP), which completed the sequencing of human DNA in 2003, promises designer cures for all manner of diseases via drugs tailor-made for the individual according to his or her genetic makeup.
Reductionism, however, has its limitations. Many mainstream psychologists rue the day when the reductionist behaviorism of J. B. Watson and B. F. Skinner hijacked the discipline of psychology, setting the field back, some estimate, by 50 years. Is a human being--one who bristles at injustice, weeps at Pachelbel's Canon, loves her children, is awestruck by beauty, and craves chocolate -- simply the product of Pavlov's conditioned reflexes to stimuli? I can't help but think fondly of my mother-in-law, who passed away to kidney failure at just 68 years of age following a series of strokes. While Harriett grappled with the prospect of either a lifetime of dialysis or of letting go, a parade of medical specialists came and went, each treating a different organ, and each leaving Harriett more bereft. It was the rehab specialist, an MD trained originally as a nurse and adept at ministering to the whole person, who meant the most to Harriet in her final days.
Reductionist models can be valuable, but at best they crudely approximate reality. In 2011, two colleagues and I published (Computer Physics Communications, Vol. 182) a novel procedure for solving the classic n-body problem, which asks: What are the trajectories of n mutually gravitating bodies? For grins, we applied the new algorithm to evolve our solar system three million years into the future. The nagging uncertainty among astronomers regarding the long-term stability of our planetary system motivated the test case. Could gravitational forces gang up years hence to eject a planet and collapse the system? Happily, our simulation corroborated the results of others: a stable status quo persists for at least another few million years.
Now the disclaimer. We considered a system comprised of just 10 bodies, the sun and 9 planets (including Pluto). All moons were excluded from the calculation, as were asteroids, relativistic effects, and the weak gravitational influences of distant galaxies. You have to draw a line somewhere, and we drew it at n=10. With more effort, we could have drawn the line at n=1000, or with a lot more effort at n=1,000,000 or more. The point is: short of n being the number of bodies in the universe, the model is incomplete, and one or more of those disregarded bodies could ultimately upset the apple cart, that is, the stability of the solar system.
Consider also the second law of thermodynamics, which states that entropy (disorder) cannot decrease in an isolated system (one that can exchange neither energy nor matter with its surroundings). Thus, a type of reductionism occupies the very heart of thermodynamics by allowing us, in principle, to wall off a system from its environment. But truly isolated systems are hard to find. Mercifully, the earth is not isolated because of the great flux of radiant energy we receive from the sun (as well as the occasional meteor that adds to the earth's mass, such as the one that recently rocked Chelyabinsk, Russia). In truth, isolated systems are nonexistent idealizations; no real system can be hermetically sealed from all outside influences. Perhaps the only truly isolated system is the entire cosmos, for as Muir observed (above), everything is "hitched to everything else."
For some, the sequencing of the human genome in 2003 -- spectacular as it was -- evoked a sense of letdown. For all their efforts, what had researchers gleaned about being human? Not much initially (except that humans have far fewer genes than anticipated). Some found the accomplishment hollow, likening it to the completion of a phone directory for New York City. Having all those names and addresses reveals nothing about the interactions of the persons listed.
Perhaps the HGP's great accomplishment, however, lay in exposing the importance of biology's newest frontier: epigenetics, the science of gene expression. It's not enough to know the genome. Genes encode heritable traits, but only if those genes are activated, or "expressed." Although identical twins begin life with identical genomes, by old age their genetic makeup may differ by 50 percent or more. All manner of environment factors -- lifestyle, diet, habits, exercise -- affect gene expression. Epigenetics has revived the old nature-nurture debate. What we become depends literally upon all that happens to us over a lifetime. Genes alone do not make an individual; it takes an ecosystem.
In 1991, Michael Talbot published The Holographic Universe. Based upon the insights into quantum entanglement by University of London physicist David Bohm and the neurophysiology of Stanford University's Karl Pribram, The Holographic Universe presents a paradigm-shifting view of the nature of reality by which the whole is contained in every part. The book's title comes from the remarkable properties of holograms, three-dimensional images constructed by laser interference and stored on two-dimensional film. Unlike conventional photographic negatives, however, each tiny piece of holographic film encodes the entire three-dimensional image!
Holography is a fitting metaphor for what mystics have always taught: separation is illusion. The universe is a seamless whole. Reductionism has revealed much, but its utility may have run its course. I anticipate that holism has as great a role to play in the future of science as reductionism has played in its past.
The final two posts in this series will address science's most stubborn assumption: materialism.