The Grand Design Page 2
The Ionians were but one of many schools of ancient Greek philosophy, each with different and often contradictory traditions. Unfortunately, the Ionians’ view of nature—that it can be explained through general laws and reduced to a simple set of principles—exerted a powerful influence for only a few centuries. One reason is that Ionian theories often seemed to have no place for the notion of free will or purpose, or the concept that gods intervene in the workings of the world. These were startling omissions as profoundly unsettling to many Greek thinkers as they are to many people today. The philosopher Epicurus (341 BC–270 BC), for example, opposed atomism on the grounds that it is “better to follow the myths about the gods than to become a ‘slave’ to the destiny of natural philosophers.” Aristotle too rejected the concept of atoms because he could not accept that human beings were composed of soulless, inanimate objects. The Ionian idea that the universe is not human-centered was a milestone in our understanding of the cosmos, but it was an idea that would be dropped and not picked up again, or commonly accepted, until Galileo, almost twenty centuries later.
As insightful as some of their speculations about nature were, most of the ideas of the ancient Greeks would not pass muster as valid science in modern times. For one, because the Greeks had not invented the scientific method, their theories were not developed with the goal of experimental verification. So if one scholar claimed an atom moved in a straight line until it collided with a second atom and another scholar claimed it moved in a straight line until it bumped into a cyclops, there was no objective way to settle the argument. Also, there was no clear distinction between human and physical laws. In the fifth century BC, for instance, Anaximander wrote that all things arise from a primary substance, and return to it, lest they “pay fine and penalty for their iniquity.” And according to the Ionian philosopher Heraclitus (ca. 535 BC–ca. 475 BC), the sun behaves as it does because otherwise the goddess of justice will hunt it down. Several hundred years later the Stoics, a school of Greek philosophers that arose around the third century BC, did make a distinction between human statutes and natural laws, but they included rules of human conduct they considered universal—such as veneration of God and obedience to parents—in the category of natural laws. Conversely, they often described physical processes in legal terms and believed them to be in need of enforcement, even though the objects required to “obey” the laws were inanimate. If you think it is hard to get humans to follow traffic laws, imagine convincing an asteroid to move along an ellipse.
This tradition continued to influence the thinkers who succeeded the Greeks for many centuries thereafter. In the thirteenth century the early Christian philosopher Thomas Aquinas (ca. 1225–1274) adopted this view and used it to argue for the existence of God, writing, “It is clear that [inanimate bodies] reach their end not by chance but by intention…. There is therefore, an intelligent personal being by whom everything in nature is ordered to its end.” Even as late as the sixteenth century, the great German astronomer Johannes Kepler (1571–1630) believed that planets had sense perception and consciously followed laws of movement that were grasped by their “mind.”
The notion that the laws of nature had to be intentionally obeyed reflects the ancients’ focus on why nature behaves as it does, rather than on how it behaves. Aristotle was one of the leading proponents of that approach, rejecting the idea of science based principally on observation. Precise measurement and mathematical calculation were in any case difficult in ancient times. The base ten number notation we find so convenient for arithmetic dates back only to around AD 700, when the Hindus took the first great strides toward making that subject a powerful tool. The abbreviations for plus and minus didn’t come until the fifteenth century. And neither the equal sign nor clocks that could measure times to the second existed before the sixteenth century.
Aristotle, however, did not see problems in measurement and calculation as impediments to developing a physics that could produce quantitative predictions. Rather, he saw no need to make them. Instead, Aristotle built his physics upon principles that appealed to him intellectually. He suppressed facts he found unappealing and focused his efforts on the reasons things happen, with relatively little energy invested in detailing exactly what was happening. Aristotle did adjust his conclusions when their blatant disagreement with observation could not be ignored. But those adjustments were often ad hoc explanations that did little more than paste over the contradiction. In that manner, no matter how severely his theory deviated from actuality, he could always alter it just enough to seem to remove the conflict. For example, his theory of motion specified that heavy bodies fall with a constant speed that is proportional to their weight. To explain the fact that objects clearly pick up speed as they fall, he invented a new principle—that bodies proceed more jubilantly, and hence accelerate, when they come closer to their natural place of rest, a principle that today seems a more apt description of certain people than of inanimate objects. Though Aristotle’s theories often had little predictive value, his approach to science dominated Western thought for nearly two thousand years.
The Greeks’ Christian successors rejected the idea that the universe is governed by indifferent natural law. They also rejected the idea that humans do not hold a privileged place within that universe. And though the medieval period had no single coherent philosophical system, a common theme was that the universe is God’s dollhouse, and religion a far worthier study than the phenomena of nature. Indeed, in 1277 Bishop Tempier of Paris, acting on the instructions of Pope John XXI, published a list of 219 errors or heresies that were to be condemned. Among the heresies was the idea that nature follows laws, because this conflicts with God’s omnipotence. Interestingly, Pope John was killed by the effects of the law of gravity a few months later when the roof of his palace fell in on him.
The modern concept of laws of nature emerged in the seventeenth century. Kepler seems to have been the first scientist to understand the term in the sense of modern science, though as we’ve said, he retained an animistic view of physical objects. Galileo (1564–1642) did not use the term “law” in his most scientific works (though it appears in some translations of those works). Whether or not he used the word, however, Galileo did uncover a great many laws, and advocated the important principles that observation is the basis of science and that the purpose of science is to research the quantitative relationships that exist between physical phenomena. But the person who first explicitly and rigorously formulated the concept of laws of nature as we understand them was René Descartes (1596–1650).
Descartes believed that all physical phenomena must be explained in terms of the collisions of moving masses, which were governed by three laws—precursors of Newton’s famous laws of motion. He asserted that those laws of nature were valid in all places and at all times, and stated explicitly that obedience to these laws does not imply that these moving bodies have minds. Descartes also understood the importance of what we today call “initial conditions.” Those describe the state of a system at the beginning of whatever interval of time over which one seeks to make predictions. With a given set of initial conditions, the laws of nature determine how a system will evolve over time, but without a specific set of initial conditions, the evolution cannot be specified. If, for example, at time zero a pigeon directly overhead lets something go, the path of that falling object is determined by Newton’s laws. But the outcome will be very different depending on whether, at time zero, the pigeon is sitting still on a telephone wire or flying by at 20 miles per hour. In order to apply the laws of physics one must know how a system started off, or at least its state at some definite time. (One can also use the laws to follow a system backward in time.)
With this renewed belief in the existence of laws of nature came new attempts to reconcile those laws with the concept of God. According to Descartes, God could at will alter the truth or falsity of ethical propositions or mathematical theorems, but not nature. He believed that God ordained the laws
of nature but had no choice in the laws; rather, he picked them because the laws we experience are the only possible laws. This would seem to impinge on God’s authority, but Descartes got around that by arguing that the laws are unalterable because they are a reflection of God’s own intrinsic nature. If that were true, one might think that God still had the choice of creating a variety of different worlds, each corresponding to a different set of initial conditions, but Descartes also denied this. No matter what the arrangement of matter at the beginning of the universe, he argued, over time a world identical to ours would evolve. Moreover, Descartes felt, once God set the world going, he left it entirely alone.
A similar position (with some exceptions) was adopted by Isaac Newton (1643–1727). Newton was the person who won widespread acceptance of the modern concept of a scientific law with his three laws of motion and his law of gravity, which accounted for the orbits of the earth, moon, and planets, and explained phenomena such as the tides. The handful of equations he created, and the elaborate mathematical framework we have since derived from them, are still taught today, and employed whenever an architect designs a building, an engineer designs a car, or a physicist calculates how to aim a rocket meant to land on Mars. As the poet Alexander Pope said:
Nature and Nature’s laws lay hid in night:
God said, Let Newton be! and all was light.
Today most scientists would say a law of nature is a rule that is based upon an observed regularity and provides predictions that go beyond the immediate situations upon which it is based. For example, we might notice that the sun has risen in the east every morning of our lives, and postulate the law “The sun always rises in the east.” This is a generalization that goes beyond our limited observations of the rising sun and makes testable predictions about the future. On the other hand, a statement such as “The computers in this office are black” is not a law of nature because it relates only to the computers within the office and makes no predictions such as “If my office purchases a new computer, it will be black.”
Our modern understanding of the term “law of nature” is an issue philosophers argue at length, and it is a more subtle question than one may at first think. For example, the philosopher John W. Carroll compared the statement “All gold spheres are less than a mile in diameter” to a statement like “All uranium-235 spheres are less than a mile in diameter.” Our observations of the world tell us that there are no gold spheres larger than a mile wide, and we can be pretty confident there never will be. Still, we have no reason to believe that there couldn’t be one, and so the statement is not considered a law. On the other hand, the statement “All uranium-235 spheres are less than a mile in diameter” could be thought of as a law of nature because, according to what we know about nuclear physics, once a sphere of uranium-235 grew to a diameter greater than about six inches, it would demolish itself in a nuclear explosion. Hence we can be sure that such spheres do not exist. (Nor would it be a good idea to try to make one!) This distinction matters because it illustrates that not all generalizations we observe can be thought of as laws of nature, and that most laws of nature exist as part of a larger, interconnected system of laws.
In modern science laws of nature are usually phrased in mathematics. They can be either exact or approximate, but they must have been observed to hold without exception—if not universally, then at least under a stipulated set of conditions. For example, we now know that Newton’s laws must be modified if objects are moving at velocities near the speed of light. Yet we still consider Newton’s laws to be laws because they hold, at least to a very good approximation, for the conditions of the everyday world, in which the speeds we encounter are far below the speed of light.
If nature is governed by laws, three questions arise:
What is the origin of the laws?
Are there any exceptions to the laws, i.e., miracles?
Is there only one set of possible laws?
These important questions have been addressed in varying ways by scientists, philosophers, and theologians. The answer traditionally given to the first question—the answer of Kepler, Galileo, Descartes, and Newton—was that the laws were the work of God. However, this is no more than a definition of God as the embodiment of the laws of nature. Unless one endows God with some other attributes, such as being the God of the Old Testament, employing God as a response to the first question merely substitutes one mystery for another. So if we involve God in the answer to the first question, the real crunch comes with the second question: Are there miracles, exceptions to the laws?
Opinions about the answer to the second question have been sharply divided. Plato and Aristotle, the most influential ancient Greek writers, held that there can be no exceptions to the laws. But if one takes the biblical view, then God not only created the laws but can be appealed to by prayer to make exceptions—to heal the terminally ill, to bring premature ends to droughts, or to reinstate croquet as an Olympic sport. In opposition to Descartes’s view, almost all Christian thinkers maintained that God must be able to suspend the laws to accomplish miracles. Even Newton believed in miracles of a sort. He thought that the orbit of the planets would be unstable because the gravitational attraction of one planet for another would cause disturbances to the orbits that would grow with time and would result in the planets either falling into the sun or being flung out of the solar system. God must keep on resetting the orbits, he believed, or “wind the celestial watch, lest it run down.” However, Pierre-Simon, marquis de Laplace (1749–1827), commonly known as Laplace, argued that the perturbations would be periodic, that is, marked by repeated cycles, rather than being cumulative. The solar system would thus reset itself, and there would be no need for divine intervention to explain why it had survived to the present day.
It is Laplace who is usually credited with first clearly postulating scientific determinism: Given the state of the universe at one time, a complete set of laws fully determines both the future and the past. This would exclude the possibility of miracles or an active role for God. The scientific determinism that Laplace formulated is the modern scientist’s answer to question two. It is, in fact, the basis of all modern science, and a principle that is important throughout this book. A scientific law is not a scientific law if it holds only when some supernatural being decides not to intervene. Recognizing this, Napoleon is said to have asked Laplace how God fit into this picture. Laplace replied: “Sire, I have not needed that hypothesis.”
Since people live in the universe and interact with the other objects in it, scientific determinism must hold for people as well. Many, however, while accepting that scientific determinism governs physical processes, would make an exception for human behavior because they believe we have free will. Descartes, for instance, in order to preserve the idea of free will, asserted that the human mind was something different from the physical world and did not follow its laws. In his view a person consists of two ingredients, a body and a soul. Bodies are nothing but ordinary machines, but the soul is not subject to scientific law. Descartes was very interested in anatomy and physiology and regarded a tiny organ in the center of the brain, called the pineal gland, as the principal seat of the soul. That gland, he believed, was the place where all our thoughts are formed, the wellspring of our free will.
Do people have free will? If we have free will, where in the evolutionary tree did it develop? Do blue-green algae or bacteria have free will, or is their behavior automatic and within the realm of scientific law? Is it only multicelled organisms that have free will, or only mammals? We might think that a chimpanzee is exercising free will when it chooses to chomp on a banana, or a cat when it rips up your sofa, but what about the roundworm called Caenorhabditis elegans—a simple creature made of only 959 cells? It probably never thinks, “That was damn tasty bacteria I got to dine on back there,” yet it too has a definite preference in food and will either settle for an unattractive meal or go foraging for something better, depending on recent experience. Is
that the exercise of free will?
Though we feel that we can choose what we do, our understanding of the molecular basis of biology shows that biological processes are governed by the laws of physics and chemistry and therefore are as determined as the orbits of the planets. Recent experiments in neuroscience support the view that it is our physical brain, following the known laws of science, that determines our actions, and not some agency that exists outside those laws. For example, a study of patients undergoing awake brain surgery found that by electrically stimulating the appropriate regions of the brain, one could create in the patient the desire to move the hand, arm, or foot, or to move the lips and talk. It is hard to imagine how free will can operate if our behavior is determined by physical law, so it seems that we are no more than biological machines and that free will is just an illusion.
While conceding that human behavior is indeed determined by the laws of nature, it also seems reasonable to conclude that the outcome is determined in such a complicated way and with so many variables as to make it impossible in practice to predict. For that one would need a knowledge of the initial state of each of the thousand trillion trillion molecules in the human body and to solve something like that number of equations. That would take a few billion years, which would be a bit late to duck when the person opposite aimed a blow.