To cite just two examples: First, in ordering sensory data, the human mind operates primarily as a machine for recognizing patterns. We then try to explain such patterns by telling sensible stories about their origin and meaning. But random systems always generate apparent patterns as a fundamental consequence of their definition. For example, we think that we see meaningful clumpings of stars in the sky, and we then name the clumps as constellations with appended stories, because stars are actually distributed at random with respect to the earth’s position in space. (To produce a sky without such clumping, stars would have to space themselves out according to rigid rules of deterministic order. We would all, to cite a clinching analogy, recognize that a series of coin flips repeating head after tail in endless and invariable order—HTHTHTHT ad infinitum—could not be the work of an honest coin and flipper, even though the sum total of each result stands at 50-50, because truly random sequences must include runs of the same outcome. Every once in awhile—in fact 1 time in 32 sequences on average—we should flip five heads in a row with an honest coin.) Therefore, since we tend to misread any clumping within random sequences as a meaningful pattern with deterministic causes, our forecasts about the future of complex systems usually rest upon false extrapolations from causes proposed as explanations for truly random results.
Second, since prediction must extend from things known to futures unknown, our prowess in forecasting falls victim to the bias that Bacon himself identified as the foremost tribal idol: our tendency to make false extrapolations from the limited world we know (that is, the realm of our own bodily size and time, of objects a few feet tall that endure for a few decades) into the universal vastness of space and time—that is, to numerous realms at disparate scales that must operate under different principles and regularities. I doubt, for example, that we really know how to think about subjects so foreign to our experience that we must label them inadequately with such terms as infinity or eternity. (Is the “big bang” the true beginning of this known universe, or have we even managed to pose such a question about origins properly? Is the concept of a beginning appropriate at all at such vast scales, even though our own lives in our limited world lead us to the [probably] fallacious notion that all material bodies must begin and end somewhere.)
Jorge Luis Borges, who greatly admired Bacon, epitomized this dilemma in his brilliant story “Averroes’s Search” about the fruitless quest of this greatest medieval Islamic commentator on Aristotle to grasp the meaning of two common terms in the master’s writings—tragedy and comedy—that had no conceivable reference or analogy in Averroes’s own surrounding culture. What similarly unavailable concepts would we need to formulate as guides to better predictions about the future of complex systems?
But the second—the external—reason for principled unpredictability trumps any internal factor in its inevitability. For even if we could smash all tribal idols and tune our brains to read external reality with complete fidelity and accuracy, we still wouldn’t be able to predict the future state of complex systems because those systems themselves do not unfold in a deterministic manner through time. Even Laplace’s all-knowing demon—the hypothetical creature who understands all nature’s laws and who recorded the position and motion of every particle in the universe at some past moment—could not specify the configuration of any world to come because too much irreducible randomness intrudes upon, and mingles with, the genuine lawfulness of many broad regularities in nature.
The excitement generated in the last decade by such concepts as chaos theory, nonlinear dynamics, bifurcation, and fractal geometry records only one aspect (the weaker one, at that) of this external argument for principled unpredictability. For these new ideas accept the premise of Laplacian determinism but then illustrate the hopelessness of supposing that we could ever become precise predictors in such a deterministic world. Most of Laplace’s mathematics yielded a gentle and orderly universe, with magnitude of effects neatly scaled to strength of causes, and with growths and declines following gradual and continuous pathways. But the mathematics of chaos theory generates such rambunctious phenomena as sudden bifurcations and overturns, and astonishingly disparate outcomes cascading from nothing but a difference in initial conditions so tiny that the most precise instruments imaginable still could not measure the distinction between two sequences at their starting points.
Thus, even if nature did operate deterministically (implying predictability in principle for an all-knowing Laplacian demon), real humans would still be utterly unable to make complete predictions in a world operating by the mathematics of chaos theory (indeed, we could not even come close, given the cascading differences that spread out from unmeasurably small distinctions between the starting points of two systems). But a much stronger argument for principled unpredictability, also pervades the natural world—the argument that conquers Laplace’s demon and tosses him into the same box that we humans must inhabit.
I do recognize that this crucial issue lies more in the domain of philosophy than of science—for I speak of a vital question that we can formulate but cannot answer by appeals to data from the empirical world (that is, from the domain accessible to science). The unpredictability implied by chaos theory arises from principled and insurmountable limitations upon our observational abilities in a deterministic world where initial conditions (that we cannot know and specify) really do imply definite outcomes. But what if the real world also includes a large component of genuine and irreducible randomness in the strong (or ontological) sense—that is, randomness at the core of the very nature of things, and not merely recorded in our inability to state and characterize the conditions that would make prediction possible. (Properties rooted in the true, external nature of things are called ontological; whereas features based on how we must observe and learn about things are epistemological. The first argument based on chaos theory defends epistemological randomness; this second argument about irreducible chance in nature invokes ontological randomness. Most people would regard the ontological argument as stronger in principle for making claims about the genuine nature of things rather than necessary pathways to human knowledge.)
And yet, in a way that can only be called funny (in the deep sense of that word, meaning curious in provoking our attention and intrigue, rather than merely tickling our funny bone), principled unpredictability wins big by either argument. And since both arguments are probably valid (with the history of the universe including a good deal of genuinely irreducible randomness mixed with determined outcomes that we cannot know, or even come close to predicting), nature indulges in overkill with a double whammy to slay the old Laplacian hope for sensible and predictable order in a deterministic world.
I don’t think that any deeper or more important principle pervades nature, and lies at the heart of all historical sequences, than this central but underappreciated notion of “contingency”—the great and liberating truth that tiny inputs, virtually invisible and risibly impotent in appearance at the outset, can cause history to cascade down any route in a vast array of entirely different pathways. And since we cannot know, control, anticipate or specify the effectively infinite range of such inputs, the future states of complex natural systems become unpredictable in principle. This fundamental property of nature has been better understood by poets and painters than by scientists, who have generally been bamboozled by the Laplacian boast (and by a false inference that the predictability of such simple phenomena as the timing of eclipses or the crystal structure of quartz could be extended to such complex historical sequences as the evolutionary pathways of life’s history or the growth of Christianity from such inauspicious beginnings). The literary world has even proposed a motto for this principle: “the kingdom lost for want of a horseshoe nail.”
This principle of contingency also operates in a fractal manner at all scales of nature—from the peculiarities of each individual organism (the lucky sperm, the one in several million, that made you, compared with the loser that, for no reas
on beyond history’s accidents, would have penetrated the egg a fraction of a millisecond later and generated a sibling of opposite sex) to the broadest patterns of the history of life (would vertebrates ever have evolved on land if one peculiar and rather marginal group of fishes had not developed fins of unusual construction, probably used for scuttling along the bottoms of ponds, that could be converted to stout supports—whereas the fins of “ordinary” fishes could not be so altered—for a creature denied the benefits of buoyancy and now exposed to forces of gravity on land?).
Moreover, this principle of contingency should not generate the feeling of despair so often evoked by a common misunderstanding. Contingency does not relegate the study of history to impotence, to mere description without potential for general understanding, or to Henry Ford’s dismissive definition as “one damn thing after another.” Principled unpredictability emerges as a fascinating property of nature, not as a limitation of our ability to understand. We cannot predict the future because nature works in such an interesting and complex manner; but we can explain the past with all the scientific rigor applied to any conventional subject in Laplace’s arsenal, provided that enough particular evidence has survived to specify the contingent inputs that caused the unpredictable cascades on one actualized path among innumerable, perfectly reasonable, but unrealized, alternatives.
I, for one, prefer the detailed beauty, richness, and surprise of unpredictable (but eminently sensible and fully explainable) history to the dull repetitions of simple systems controlled by so few variables, and manifesting such a limited range of possible states, that we can know the ever-cycling pathways in advance. Thus, I resonate with the final sentence of Darwin’s Origin of Species, where this blessedly genial, but sly and tough-minded, man extolled the fascination of evolutionary biology over Newtonian physics by contrasting life’s wondrously meandering rise and spread with the unchanging regularities of planetary motion:
There is grandeur in this view of life … and whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.
Finally, this principle of contingency underlies the liberation (but also the fear, and the responsibility) that emerges from the deep natural truth inherent in the concept that our language calls “free will.” Every individual human life, however insignificant each of us may feel before the immense grandeur of the cosmos and the almost inconceivable depth of time, can truly make a profound difference. Any of us might provoke (although few of us actually will) one of those bifurcations, those cascades, those catastrophes that chaos theory describes, and that make history. With less grandiosity, but with universal potential, each of us can exert a profound and beneficial effect upon the lives of a few people to whom we direct our love and care. And in any case, as Milton said in his most beautiful line—a statement made, no doubt, for a primary theological motive but brought to fullest actualized meaning by the principle of contingency—“they also serve who only stand and wait.”
Contingency does not deny all predictability for any aspect of complex historical sequences. Broad features can be specified with reasonable confidence, if only because laws of nature cannot be set aside or overridden—so humans need not fear a measurable probability of projection into orbit every time they jump under their own power alone; ecosystems will evolve with more biomass in prey than in predators, even though we cannot predict the actual creatures destined to fulfill these roles in any particular case; and the sun (if left to run its full course of potential life based on its own fuel supply) will continue to burn for several billion years, thus allowing the contingent history of life to continue along its wondrously unpredictable pathways for a long time to come.
Our struggle, as scientists, lies in determining where to place the boundary between these domains of predictability for broad aspects and contingency for details. I would only add that, in the arrogance of our past assumption that humans represent a predictable pinnacle of life’s necessarily progressive advance, and that our species therefore rules this planet by natural right, we have made the fatal mistake of assuming that we represent one of the broad aspects, whereas we truly belong smack in the center of the domain of details—along with every other individual species that has ever evolved among the billions brought into being during the history of life on this planet (not to mention the potential gazillions that never happened to originate along the contingent pathways of actual history).
Homo sapiens marks a particularly fascinating detail in the history of evolution on earth, a tiny, unpredictable, accidental, and late-arising little twig on the luxuriously arborescent bush of life’s history. Particularly fascinating, endowed with unprecedented power to alter ourselves and our planet’s course for good or for evil—but a detail nonetheless, and therefore subject to analysis within the domain of contingency. We may pose our questions in the broadest terms of abstract philosophy, but when we push through these formulations to the core of our concerns, we are really asking about ourselves, and our prospects in this vale of tears that human wisdom could so greatly alleviate, and perhaps even raise to a broad meadow of bounty—the only general forecast about possibilities (not guarantees) that anyone can reasonably advance. And since we reside in the domain of contingency, our deep questions dwell with us there as well.
Thus, the inherent contingency of our existence and history, and the requisite modesty that such an understanding should generate, permits no confident forecasting about human and planetary futures in the vast realm of detail that motivates nearly all our social and scientific questions, and our moral dilemmas as well. We may forecast, from the broad domain of lawlike predictability, that the earth will endure for a few billion additional years until the sun spends its fuel. But we cannot know how our lives and loves will be faring even halfway through the first century of our new millennium.
I once posed the following “thought question” to a prominent colleague in evolutionary biology: “If you owned a time machine and could visit any single point in history, past or future, where would you choose to go?” My paleontological thoughts went only to the grand moments of life’s history—send me, I said, into the heart of the Cambrian explosion, or into the latest Cretaceous earth as an extraterrestrial body smashed into the planet, triggering the extinction of dinosaurs and giving mammals a contingent opportunity that did, in fact, eventually generate the improbable twig of Homo sapiens. But my colleague said, with great wisdom that shamed my own too obvious, and therefore pedestrian, choice: “No, just set me down for one moment in New York City fifty years from today. I just want to see if it’s still there. From that single nugget of information, everything I need to know will follow.”
At most—and this far into the realm of possibilities we can certainly venture—we may advocate for our future an attitude that I call “tragic optimism.” Our contingent mental power, and our woefully imperfect, but by no means inactive, moral sensibilities, give us an opportunity—but never a guarantee—to prevail with decency and maximal benefit to fellow humans. But we usually gear ourselves into action far too late to avert a great deal of actual suffering that could have been forestalled if only we had followed the precept of contingency discussed earlier (see this page): since we cannot know the future, we should move early and proactively to avert potential disasters.
Under tragic optimism, for example, we can now prevent famines—for the earth has always provided enough food at any moment, whereas local droughts and pestilences, combined with failures in distribution, have led to regional starvation. We could not, even in principle, make such distributions in the past (or even always know where famine had taken hold), but advances in communication and transportation surely allow us to do so now—and in this power lies the potential liberating force of science. But, tragically, we usually act too late—soon enough to prevent the extirpation of an entire population, but not until the preventable deaths and sufferi
ng of so many fellow humans alert us to the problem, awaken our slothful moral sensibilities, and impel us to proper action.
What more can we ask of contingency than the chance to prevail—and to prevail with decency. And what more could we desire beyond this greatest and most stimulating of all possible challenges, this most precious opportunity that evolution has vouchsafed to the only conscious species that 3.5 billion years of life’s history has ever generated. In this hope lies our liberation and our responsibility. I therefore close with the wise words of a great, but underappreciated, scientist—the early nineteenth-century Scottish mathematician and geologist John Playfair who, in 1814, wrote of the future and our potential to make it right: “It were unwise to be sanguine, and unphilosophical to despair.”
PREFACE
TO THE ORIGINAL EDITION
OUR PRECISELY ARBITRARY MILLENNIUM
I began to think about this book during the first week of January 1950. I was eight years old, and a good part of my life revolved around the simple pleasures of weekly rituals. On Sundays, I would pull out The New York Times sports section and turn to the agate-type listings of performance records for major league baseball players. I would take an index card, align all the stats for a single player along the top edge, and then slowly move the card down, a player at a time, studying the numerical data for each in turn.
The weekly arrival of Life magazine, that quintessential organ of middlebrow culture, defined a second activity—this time a less structured survey of pictures. The first issue for 1950 hit me with a force that I still don’t comprehend, and burned into my cortex a permanent memory as potent and enduring as the records of childhood’s more tumultuous events—my kid brother’s birth, my father’s return from war. This first issue for 1950 marked the halfway point of the twentieth century by evaluating what had happened and predicting what the second segment might bring. (The publication of this special issue in January 1950, rather than January 1951—the “true” half-century point, according to one school of thought—provides yet another expression of that recurring, perverse, frustrating, funny, yet somehow fascinating debate on the unresolvable issue of when centuries end, the subject of Part 2 in this book and the source of more passionate discussion than ever before, because the forthcoming passage also marks the inception of a new millennium.)
Questioning the Millennium Page 2