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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
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