geoffrey_west's picture
Theoretical Physcicist; Shannan Distinguished Professor and Past President, Santa Fe Institute; Author, Scale: The Universal Laws of Growth, Innovation, Sustainability, and the Pace of Life in Organisms, Cities, Economies, and Companies
The Theory of Everything

Everything? Well, wait a minute. Questioning A Theory of Everything may be beating a dead horse since I’m certainly not the first to be bothered by its implicit hyperbole but let’s face it, referring to one’s field of study as The Theory of Everything smacks of arrogance and naivité. Although it’s only been around for a relatively short period and may already be dying a natural death, the phrase, though certainly not the endeavour, should be retired from serious scientific literature and discourse.

Let me elaborate. The search for grand syntheses, for commonalities, regularities, ideas and concepts that transcend the narrow confines of specific problems or disciplines is one of the great inspirational drivers of science and scientists. Arguably, it is also a defining characteristic of homo sapiens sapiens. Perhaps the binomial form of sapiens is some distorted poetic recognition of this. Like the invention of gods and God, the concept of A Theory of Everything connotes the grandest vision of all, the inspiration of all inspirations, namely that we can encapsulate and understand the entirety of the universe in a small set of precepts, in this case, a concise set of mathematical equations. Like the concept of God, however, it is potentially misleading and intellectually dangerous.

Among the classic grand syntheses in science are Newton’s laws, that taught us that heavenly laws were no different than the earthly, Maxwell’s unification of electricity and magnetism, that brought the ephemeral aether into our lives, Darwin’s theory of natural selection, which reminded us that we’re just animals and plants after all, and the laws of thermodynamics that suggest we can’t go on forever. Each of these has had profound consequences not only in changing the way we think about the world, but also in laying the foundations for technological advancements that have led to the standard of living many of us are privileged to enjoy. Nevertheless, they are all, to varying degrees, incomplete. Indeed, understanding the boundaries of their applicability, the limits to their predictive power and the ongoing search for exceptions, violations and failures have provoked even deeper questions and challenges, stimulating the continued progress of science and the unfolding of new ideas, techniques and concepts.

One of the great ongoing scientific challenges is the search for a Grand Unified Theory of the elementary particles and their interactions, including its extension to understanding the cosmos and even the origin of space-time itself. Such a theory would be based on a parsimonious set of underlying mathematisable universal principles that integrate and explain all the fundamental forces of nature from gravity and electromagnetism to the weak and strong nuclear forces, incorporating Newton’s laws, quantum mechanics and general relativity. Fundamental quantities like the speed of light, the dimensionality of space-time and masses of the elementary particles would all be predicted, and the equations governing the origin and evolution of the universe through to the formation of galaxies and beyond would be derived, and so on. This constitutes The Theory of Everything. It is a truly remarkable and enormously ambitious quest that has occupied thousands of researchers for over fifty years at a cost of billions of dollars. Measured by almost any metric this quest, which is still far from its ultimate goal, has been enormously successful, leading, for example, to the discovery of quarks and the Higgs, to black holes and the Big Bang, to quantum chromodynamics and string theory…..and to many Nobel Prizes.

But Everything? Well, hardly. Where’s life, where are animals and cells, brains and consciousness, cities and corporations, love and hate, etc, etc? How does the extraordinary diversity and complexity seen here on earth arise? The simplistic answer is that these are inevitable outcomes of the interactions and dynamics encapsulated in the Theory. Time evolves from the geometry and dynamics of strings, the universe expands and cools, and the hierarchy from quarks to nucleons, to atoms and molecules, to cells, brains, and emotions and all the rest come tumbling out; a sort of deus ex machina, a result of "just" turning the crank of increasingly complicated equations and computations presumed, in principle, to be soluble to any sufficient degree of accuracy. Qualitatively, this extreme version of reductionism may have some validity, but Something is missing.

The "Something" includes concepts like information, emergence, accidents, historical contingency, adaptation and selection, all characteristics of complex adaptive systems whether organisms, societies, ecosystems or economies. These are composed of myriad individual constituents or agents that take on collective characteristics that are generally unpredictable, certainly in detail, from their underlying components even if the interactive dynamics are known. Unlike the Newtonian paradigm upon which The Theory of Everything is based, the complete dynamics and structure of complex adaptive systems cannot be encoded in a small number of equations. Indeed, in most cases, probably not even in an infinite number! Furthermore, predictions to arbitrary degrees of accuracy are not possible, even in principle.

Perhaps, then, the most surprising consequence of a visionary Theory of Everything is that it implies that, on the grand scale, the universe, including its origins and evolution, though extremely complicated, is not complex but, in fact, is surprisingly simple since it can be encoded in a limited number of equations, conceivably only one. This is in stark contrast to here on earth where we are integral to some of the most diverse, complex and messy phenomena that occur anywhere in the universe, and which require additional, possibly non-mathematisable concepts, to understand. So, while applauding and admiring the search for a Grand Unified Theory of all the basic forces of nature, let’s drop the implication that it can, in principle, explain and predict Everything. Let us instead incorporate a parallel quest for A Grand Unified Theory of Complexity. The challenge of developing a quantitative, analytic, principled, predictive framework for understanding complex adaptive systems is surely a grand challenge for the 21st Century. Like all grand syntheses, it will inevitably remain incomplete but nevertheless will undoubtedly inspire significant, possibly revolutionary, new ideas, concepts, and techniques.