Sample text for The end of certainty : time, chaos, and the new laws of nature / Ilya Prigogine ; in collaboration with Isabelle Stengers.


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Excerpt from Chapter 1

Is the universe ruled by deterministic laws? What is the nature of time? These questions were formulated by the pre-Socratics at the very start of Western rationality. After more than twenty-five hundred years, they are still with us. However, recent developments in physics and mathematics associated with chaos and instability have opened up different avenues of investigation. We are beginning to see these problems, which deal with the very position of mankind in nature, in a new light, and can now avoid the contradictions of the past.

The Greek philosopher Epicurus was the first to address a fundamental dilemma. As a follower of Democritus, he believed that the world is made of atoms and the void. Moreover, he concluded, atoms fall through the void at the same speed and on parallel paths. How then could they collide? How could novelty associated with combinations of atoms ever appear? For Epicurus, the problems of science, the intelligibility of nature, and human destiny could not be separated. What could be the meaning of human freedom in a deterministic world of atoms? As Epicurus wrote to Meneceus, "Our will is autonomous and independent and to it we can attribute praise or disapproval. Thus, in order to keep our freedom, it would have been better to remain attached to the belief in gods rather than being slaves to the fate of the physicists: The former gives us the hope of winning the benevolence of deities through promise and sacrifices; the latter, on the contrary, brings with it an inviolable necessity." How contemporary this quotation sounds! Again and again, the greatest thinkers in Western tradition, such as Immanuel Kant, Alfred North Whitehead, and Martin Heidegger, felt that they had to make a tragic choice between an alienating science or an antiscientific philosophy. They attempted to find some compromise, but none proved to be satisfactory.

Epicurus thought that he had found a solution to this dilemma, which he termed the clinamen. As expressed by Lucretius, "While the first bodies are being carried downwards by their own weight in straight lines through the void, at times quite uncertain and at uncertain places, they deviate slightly from their course, just enough to be defined as having changed direction." 2 But no mechanism was given for this clinamen. No wonder that it has always been considered a foreign, arbitrary element.

But do we need this novelty at all? For Heraclitus, as understood by Popper, "Truth lies in having grasped the essential becoming of nature, i.e., having represented it as implicitly infinite, as a process in itself"3 Parmenides took the opposite view. In his celebrated poem on the unique reality of existence, he wrote, "Nor was it ever, nor will it be, since now it is, all together."4

It is amusing that the Epicurus clinamen has appeared repeatedly in the science of our century. In his classic paper on the emission of photons associated with the transitions between atomic states (1916), Einstein explicitly expressed his confidence in scientific determinism, although he assumed that these emissions are ruled by chance.

Greek philosophy was unable to solve this dilemma. Plato linked truth with being, that is, with the unchanging reality beyond becoming. Yet he was conscious of the paradoxical character of this position because it would debase both life and thought. In The Sophist, he concluded that we need both being and becoming.5

This duality has plagued Western thought ever since. As observed by the French philosopher Jean Wahl, the history of Western philosophy is, on the whole, an unhappy one, characterized by perpetual oscillations between the world as an automaton and a theology in which God governs the universe.6 Both are forms of determinism.

This debate took a turn in the eighteenth century with the discovery of the "laws of nature." The foremost example was Newton's law relating force and acceleration, which was both deterministic and, more important, time reversible. Once we know the initial conditions, we can calculate all subsequent states as well as the preceding ones. Moreover, past and future play the same role because Newton's law is invariant with respect to the time inversion to » -t. This leads to nightmares such as the demon imagined by Pierre-Simon de Laplace, capable of observing the current state of the universe and predicting its evolution.7

As is well known, Newton's law has been superseded in the twentieth century by quantum mechanics and relativity. Still, the basic characteristics of his laws -- determinism and time symmetry -- have survived. It is true that quantum mechanics no longer deals with trajectories but with wave functions (see Section IV of this chapter and Chapter 6), but it is important to note that the basic equation of quantum mechanics, Schrödinger's equation, is once again deterministic and time reversible.

By way of such equations, laws of nature lead to certitudes. Once initial conditions are given, everything is determined. Nature is an automaton, which we can control, at least in principle. Novelty, choice, and spontaneous action are real only from our human point of view.

Many historians believe that an essential role in this vision of nature was played by the Christian God as conceived in the seventeenth century as an omnipotent legislator. Theology and science agreed. As Gottfried von Leibniz wrote, "In the least of substances, eyes as piercing as those of God could read the whole course of things in the universe, quae sint, quae fyerint, quae mox futura trahantur" (those which are, which have been, and which shall be in the future).8 The discovery of nature's deterministic laws was thus bringing human knowledge closer to the divine, atemporal point of view.

The concept of a passive nature subject to deterministic and time-reversible laws is quite specific to the Western world. In China and Japan, nature means "what is by itself." In his excellent book Science and Society in East and West, Joseph Needham tells us of the irony with which Chinese men of letters greeted the Jesuits' announcement of the triumphs of modern science.9 For them, the idea that nature is governed by simple, knowable laws seemed to be a perfect example of anthropocentric foolishness. According to Chinese tradition, nature is spontaneous harmony; speaking about "laws of nature" would thus subject nature to some external authority.

In a message to the great Indian poet, Rabindranath Tagore, Einstein wrote:

If the moon, in the act of completing its eternal path round the earth, were gifted with self-consciousness, it would feel thoroughly convinced that it would travel its path on its own, in accordance with a resolution taken once and for all.

So would a Being, endowed with higher insight and more perfect intelligence, watching man and his doings, smile about this illusion of his that he was acting according to his own free will.

This is my belief, although I know well that it is not fully demonstrable. If one thinks out to the very last consequence what one exactly knows and understands, there would hardly be any human being who could be impervious to this view, provided his self-love did not rub up against it. Man defends himself from being regarded as an impotent object in the course of the Universe. But should the lawfulness of happenings, such as unveils itself more and more clearly in inorganic nature, cease to function in the activities in our brain?10

To Einstein, this appeared to be the only position compatible with the achievements of science. But this conclusion is as difficult to accept now as it was to Epicurus. Time is our basic existential dimension. Since the nineteenth century, philosophy has become more and more time centered, as we see in the work of Georg Wilhelm Hegel, Edmund Husserl, William James, Henri Bergson, Martin Heidegger, and Alfred North Whitehead. For physicists such as Einstein, the problem has been solved. For philosophers, it remains the central question of ontology, at the very basis of the meaning of human existence.

In The Open Universe: An Argument for Indeterminism, Popper wrote, "I regard Laplacian determinism -- confirmed as it may seem to be by the prima facie deterministic theories of physics, and by their marvelous success -- as the most solid and serious obstacle to our understanding and justifying the nature of human freedom, creativity, and responsibility." For Popper, "The reality of time and change is the crux of realism." 11

In his short essay, "The Possible and the Real," Bergson argued, "What is the role of time?... Time prevents everything from being given at once.... Is it not the vehicle of creativity and choice? Is not the existence of time the proof of indeterminism in nature?"12 For both Popper and Bergson, we need "indeterminism." But how do we go beyond determinism? This difficulty is well analyzed in an essay by William James entitled "The Dilemma of Determinism."13 In accord with well-defined mechanisms, determinism is "mathematizable," as shown by the laws of nature formulated by Newton, Schrödinger, and Einstein. In contrast, deviations from determinism seem to introduce anthropomorphic concepts such as chance or accident.

The conflict between the time-reversible view of physics and time-centered philosophy has led to an open clash. What is the purpose of science if it cannot incorporate some of the basic aspects of human experience? The anti-scientific attitude of Heidegger is well known. Already Friedrich Nietzsche had concluded that there are no facts, only interpretations. As stated by John R. Searle, postmodern philosophy, with its idea of deconstruction, challenges Western traditions regarding the nature of truth, objectivity, and reality.14 In addition, the role of evolution, of events, in our description of nature is steadily increasing. How then can we maintain a time-reversible view of physics?

In October 1994, there appeared a special issue of Scientific American devoted to "life in the universe."15 At all levels -- cosmology, geology, biology, and human society -- we see a process of evolution in regard to instabilities and fluctuations. We therefore cannot avoid the question: How are these evolutionary patterns rooted in the fundamental laws of physics? Only one article, written by the eminent physicist Steven Weinberg, is relevant to this problem. He writes, "As much as we would like to take a unified view of nature, we keep encountering a stubborn duality in the role of intelligent life in the universe, as both subject and student.... On the one hand, there is the Schrödinger equation, which describes in a perfectly deterministic way how the wave function of any system changes with time. Then, quite separate, there is a set of principles that tells how to use the wave function to calculate the probabilities of various possible outcomes when someone makes the measurement.16

Does this suggest that through our measurements, we ourselves are at the origin of cosmic evolution? Weinberg speaks of a stubborn duality, a point of view found in many recent publications such as Stephen W. Hawking's Brief History of Time.17 Here Hawking advocates a purely geometrical interpretation of cosmology. In short, time would be an accident of space. But he understands that this interpretation is not enough. We need an arrow of time to deal with intelligent life. Therefore, along with many other cosmologists, Hawking introduces the so-called anthropic

principle. Nevertheless, this principle is as arbitrary as was Epicurus' clinamen. Hawking gives no indication of how the anthropic principle could ever emerge from a static geometrical universe.

As mentioned earlier, Einstein attempted to maintain the of nature, including mankind, at the cost of reducing us to mere automata. This was also the view of Baruch Spinoza. But there was another approach suggested by Rene; Descartes, also in the seventeenth century, which involved the concept of dualism: on one side is matter, res extensa, as described by geometry, and on the other, the mund, associated with res cogitans.18 In this way, Descartes described the striking difference between the behavior of simple physical systems such as a frictionless pendulum and the functioning of the human brain. Curiously, the anthropic principle brings us back to Cartesian dualism.

In The Emperor's New Mind, Roger Penrose states, "It is our present lack of understanding of the fundamental laws of physics that prevents us from coming to grips with the concept of 'mind' in physical or logical terms."19 We believe that Penrose is right: We need a new formulation of the fundamental laws of physics. The evolutionary aspects of nature have to be expressed in terms of the basic laws of physics. Only in this way can we give a satisfactory answer to Epicurus' dilemma. The reasons for indeterminism, for temporal asymmetry, must be rooted in dynamics. Formulations that do not contain these features are incomplete, exactly as would be formulations of physics that ignore gravitation or electricity.

Probability plays an essential role in most sciences, from economics to genetics. Still, the idea that probability is merely a state of mind has survived. We now have to go a step farther and show how probability enters the fundamental laws of physics, whether classical or quantum. A new formulation of the laws of nature is now possible. In this way, we obtain a more acceptable description in which there is room for both the laws of nature and novelty and creativity.

At the beginning of this chapter, we mentioned the pre-Socratics. In fact, we owe to the ancient Greeks two ideals that have since shaped human history. The first is the intelligibility of nature, or in Whitehead's words, "the attempt to frame a coherent, logical, necessary system of general ideas in terms of which every element of our experience can be interpreted."20 The second is the idea of democracy based on the assumption of human freedom, creativity, and responsibility. As long as science led to the description of nature as an automaton, these two ideals were contradictory. It is this contradiction that we are beginning to overcome.

Copyright © 1996 by Éditions Odile Jacob




Library of Congress subject headings for this publication:
Science -- Philosophy.
Space and time.
Chaotic behavior in systems.
Natural history.