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Throughout the history of the Western world, science has possessed an extraordinary amount of authority and prestige. And while its pedestal has been jostled by numerous evolutions and revolutions, science has always managed to maintain its stronghold as the knowing enterprise that explains how the natural world works: we treat such legendary scientists as Galileo, Newton, Darwin, and Einstein with admiration and reverence because they offer profound and sustaining insight into the meaning of the universe.
In The Intelligibility of Nature, Peter Dear considers how science as such has evolved and how it has marshaled itself to make sense of the world. His intellectual journey begins with a crucial observation: that the enterprise of science is, and has been, directed toward two distinct but frequently conflated ends—doing and knowing. The ancient Greeks developed this distinction of value between craft on the one hand and understanding on the other, and according to Dear, that distinction has survived to shape attitudes toward science ever since.
Teasing out this tension between doing and knowing during key episodes in the history of science—mechanical philosophy and Newtonian gravitation, elective affinities and the chemical revolution, enlightened natural history and taxonomy, evolutionary biology, the dynamical theory of electromagnetism, and quantum theory—Dear reveals how the two principles became formalized into a single enterprise, science, that would be carried out by a new kind of person, the scientist.
Finely nuanced and elegantly conceived, The Intelligibility of Nature will be essential reading for aficionados and historians of science alike.
— Eric Ormsby
— Paticia Fara
— Adrian Barnett
— Richard Yeo
— Matthew L. Jones
— Tadeusz Aniszewski
— Robert J. Deltete
— Michael Esfield
How Science Makes Sense of the World
Copyright © 2006 The University of Chicago
All right reserved.
The Mechanical Universe from Galileo to Newton
I. The World as a Machine
The seventeenth century is often described as the period in which the enterprise of modern science was born. The so-called Scientific Revolution, on this view, saw the birth in western Europe of many of the characteristic features of science as we know it today: intellectual, social, and institutional. But those latter two categories, the social and the institutional, probably owe their typical modern forms (especially the conduct of scientific research in universities) to precedents set in the nineteenth rather than the seventeenth century. Nonetheless, in the intellectual arena the importance of what happened in the seventeenth century is undeniable, because this period saw the emergence of one of the most dominant metaphors in subsequent science: the metaphor of the world as a machine.
There is nothing inevitable about seeing the world as a kind of machine. On the contrary, in cultures the world over, including most of earlier European history, the commonest way of seeing the natural world has been in terms of living organisms. In the learned cultureof premodern Europe-the culture of universities and of books-the most influential version of this view derived from the writings of the ancient Greek philosopher Aristotle. Aristotle based his approach to nature on the ways in which we tend to make sense of living processes around us. Plants and animals, as well as people, are born, grow, become old, and die. Aristotle found it natural to model his understanding of all processes in the world on these kinds of experiences. For him, therefore, behaviors in the natural world were made intelligible by understanding them as processes, directed towards a goal. An acorn sprouts, sets roots, and grows. Why? Because it is on its way to becoming an oak tree. A dog runs towards a piece of meat. Why? Because it wants to eat it. Purpose, goals, make sense of all kinds of processes in the world, just as they do in explaining the behavior of human beings, and for Aristotle these goals did not even have to rely on conscious intentions. The acorn growing towards becoming an oak tree is not conscious of an intention to do so; it just does it. But we still explain what happens in terms of how the process will usually (barring accidents) end up. This form of explanation is known in English as teleological, from the Greek word telos, meaning goal.
Teleology characterized all of Aristotle's universe. It even explained such things as why stones fall to the ground: they do so because they are seeking the center of the universe (where Aristotle located the earth itself ). This was the way in which the world of late medieval Europe, with Aristotelian philosophy entrenched in its universities, organized its natural philosophy and made sense of the world. Things and occurrences were intelligible when they could be understood in terms of processes that aimed at some purpose.
This was the natural philosophy that many educated Europeans in the seventeenth century rebelled against. The major names in philosophy and the sciences in that period, such as Descartes, Galileo, and Newton, began to criticize the idea that teleological explanations were appropriate for understanding nature, and advocated in their place explanations that privileged mechanical causation. The model would no longer be a growing organism, but a clock. By knowing the arrangement of the clock's component parts and the ways in which they pushed against each other, one could understand the characteristic movements displayed by the clock's hands. To explain the movements of the hands by reference to their purpose of displaying the right time seemed to be ridiculous. In fact, an Aristotelian philosopher would not have disagreed on that point. He would simply have regarded it as inappropriate to use a clock as the model for explaining natural phenomena. But for people like Descartes, even the growth of a plant was something to be understood in terms of inert matter in motion, analogous to clockwork.
The seventeenth-century conflict between Aristotelian philosophers and the new proponents of what was called the "mechanical philosophy" is an excellent example of radically differing views of scientific intelligibility in conflict. Each group (despite wide differences among individuals in the same camp) sought natural-philosophical understanding, but they could scarcely agree on what true understanding meant. For one group, explanations of natural phenomena in terms of mechanical interactions failed to make sense of the very processes supposedly being explained, whereas for the other group, explanations of natural phenomena in terms of teleology themselves failed to make sense. Were inanimate objects to be ascribed souls that could have desires and intentions? Aristotelians did not believe that nonliving things required souls or minds in order for their behaviors to be explained teleologically, but mechanists claimed not to understand how goal-directed behavior made any sense without them.
One of the clearest ways to see the difficulties faced by both sides is to look at how they criticized one another. The rules of engagement in this dispute were not set out clearly in advance, and the victory of one side or the other could not be determined to everyone's satisfaction by the application of formal logic. Furthermore, what was at issue had nothing to do with disagreements over what phenomena there were in the world to be explained; empirical investigation would not settle matters. In that sense, this was a fundamentally philosophical debate, and specifically a natural-philosophical one. It deeply concerned the nature of the universe, rather than resting on the affirmation or denial of controversial physical phenomena.
So a typical procedure in attacking a philosophical opponent in the seventeenth century was to ridicule him. Here is an example from one of the writings of René Descartes (1596-1650), one of the most influential of all the mechanical philosophers of the seventeenth century. In this work, written in French in the early 1630s and called The World, Descartes provided a detailed sketch of the entire physical universe, with every last feature of it to be explained in the mechanical terms of lifeless bits of matter pushing against one another, much as a human worker creates effects by pushing matter against matter (fig. 1.1). In the course of the account, Descartes pauses to criticize the standard Aristotelian explanation of what motion really is:
And trying to make it more intelligible, they [i.e. Aristotelian philosophers] have still not been able to explain it more clearly than in these terms: motus est actus entis in potentia, prout in potentia est. The terms are so obscure to me that I am compelled to leave them in Latin because I cannot interpret them. (And in fact the words "motion is the act of a being which is in potency, in so far as it is in potency" are no clearer for being in the vernacular.)
Descartes wants to reject the Aristotelian explanation of motion not on the grounds that his is preferable, or that empirical evidence disproves theirs, but simply on the grounds that their explanation makes no sense. And he does this by ridiculing them. He behaves as though he is unable to show the insufficiency of the Aristotelian account of motion by analyzing it and showing it to be faulty, or self-contradictory; instead, he appeals directly to his reader's intuitions of intelligibility.
In some circumstances, this tactic might well appear as a "know-nothing" mockery of things that the ridiculer does not himself properly understand. But Descartes, no fool and also no ignoramus, surely understood what he was attacking. In short, Descartes made fun of this piece of Aristotelian philosophy because he thought that its faults were so deep-rooted that they could not be corrected; there was no basis on which to make sense of it. So he said so.
Descartes's pretended inability to understand the meaning of this explanation of motion was, of course, not one that was shared by Aristotelian philosophers themselves. They believed that they understood it and that it was a good explanation of the phenomenon. Descartes too would, we may reasonably suppose, have been capable of restating and elaborating on the sentence that he quotes in much the same language as its supporters would have done; he would not have been dumbfounded by it. But he clearly felt that however the explanation was interpreted, it would always come down to the acceptance or rejection of something that for him simply did not make sense. Any argument about the matter was always going to end in deadlock.
Descartes played on a common expectation, of course: his confession of ignorance was evidently tailored for a reader who would have sympathy with his position. Someone who speaks from a weak or inferior position can scarcely boast of an inability to understand the opponent's arguments, and certainly not in so comprehensive a manner. Perhaps the most lucid exemplar of this kind of approach is the great polemicist Galileo Galilei (1564-1642). He used a similar ploy in a book devoted to supporting the doctrine of a moving earth, the Dialogue Concerning the Two Chief World Systems of 1632. Galileo's reader will quickly have learned that this dialogue's fictional character Salviati, who attacks Aristotle and defends Copernicus's doctrine of a moving earth, is to be applauded, while the character Simplicio, a caricature of an Aristotelian, should be seen as foolish. So when Simplicio purports to explain why bodies fall by reference to their gravity, Salviati replies by ridiculing the use of the word as an explanation. What is it that moves earthly things downwards? "The cause of this effect," says Simplicio, "is well known; everybody is aware that it is gravity." Salviati responds in this way: "You are wrong, Simplicio; what you ought to say is that everyone knows that it is called 'gravity.' What I am asking you for is not the name of the thing, but its essence, of which essence you know not a bit more than you know about the essence of whatever moves the stars around." Similarly, when the English philosopher Thomas Hobbes, a few years later, ridiculed the usual Aristotelian explanation of fall as an endeavor towards the earth's center, he wrote: "As if Stones, and Metalls had a desire, or could discern the place they would bee at, as Man does; or loved Rest, as Man does not; or that a peece of Glasse were lesse safe in the Window, than falling into the Street."
A good case can be made, however, that Aristotelian explanations like this one, involving "qualities" such as gravity that were possessed by things, were by no means as empty of content as Galileo or Hobbes tried to make out. For example, an explanation involving the quality "gravity" (i.e., "heaviness") as something that a body can possess proposes the existence of a kind of thing in the world, a real quality, that does not exist according to other ways of explaining fall. The Aristotelian position, that is, does not simply play with words, but makes claims about what sorts of things the world contains. Nonetheless, Galileo had no more fear than Descartes of being held up to ridicule by a competent philosopher, even though he misrepresented the point of his opponents' arguments. Galileo's rhetorical position was easily strong enough, because the audience that mattered was already on his side. The common assumption of Galileo and the rest seems to have been that, since (according to them) the Aristotelian arguments make no sense, an unflinching consideration of those arguments in the very words in which they are expressed will make that unintelligibility self-evident. In order, then, to convict Aristotelian explanations of failing to make sense, all that these writers can do is to pillory them; there is no other recourse.
In 1620 the English statesman and philosopher Francis Bacon (1561-1626) had written in his work New Organon, defending his own critique of Aristotelian philosophy, "There is no easy way of teaching or explaining what we are introducing; because anything new will still be understood by analogy with the old." He had earlier made a similar point: "No judgement can rightly be made of our way (one must say frankly), nor of the discoveries made by it, by means of anticipations (i.e. the reasoning currently in use); for one must not require it to be approved by the judgement of the very thing which is itself being judged." Bacon tried, that is, to prevent people from rejecting his innovations before he had a chance to present them properly. The difference in position between Bacon on the one hand and Galileo or Hobbes on the other is that the latter writers were on the offensive, and did not need to clear space to allow them to develop their own ideas. They wanted their opponents to be branded as wrong on the grounds that the arguments of those opponents made no sense, and they expected their readers to share their views. (They were also sometimes the victims of similar tactics.)
Negative arguments could only go so far, however, and Descartes in particular had his own especially systematic ways of explaining natural phenomena. The technique that he employed both in The World and in his later, fuller account of his world system, the Principles of Philosophy (published 1644) was the curious and interesting one of telling an explicitly fictional story about the origins of the universe. This story, which Descartes called a "fable," was not intended to be believed. It was meant to persuade his readers that the account he gave of how the universe currently works was a plausible one.
I want to wrap up part of it [i.e., the account] in the guise of a fable, in the course of which I hope the truth will not fail to manifest itself sufficiently clearly, and that this will be no less pleasing to you than if I were to set it forth wholly naked.
He then goes on to a "Description of a new world, and the qualities of the matter of which it is composed," so as to show that this new world could be understood perfectly by his reader, and that, furthermore, it would be indistinguishable from the real world. Descartes explained this strategy more fully in the Principles and stressed even more strongly that his description was not of the actual world at all, and that this approach had close parallels with accepted ways of investigating nature:
I shall even make some assumptions which are agreed to be false.
Indeed, in order to provide a better explanation for the things found in nature, I shall take my investigation of their causes right back to a time before the period when I believe that the causes actually came into existence. For there is no doubt that the world was created right from the start with all the perfection which it now has. The sun and earth and moon and stars thus existed in the beginning, and, what is more, the earth contained not just the seeds of plants but the plants themselves; and Adam and Eve were not born as babies but were created as fully grown people.... Nevertheless, if we want to understand the nature of plants or of men, it is much better to consider how they can gradually grow from seeds than to consider how they were created by God at the very beginning of the world.
Descartes will thus propose basic principles, or "seeds," to provide explanations that show how the things in the world could have come into being.
For although we know for sure that they never did arise in this way, we shall be able to provide a much better explanation of their nature by this method than if we merely described them as they now are. And since I believe I have in fact found such principles, I shall give a brief account of them here.
He then proceeds to give an account of the universe in which everything is explained in terms of inert pieces of matter interacting with one another by collision or direct pressure (fig. 1.2). Matter itself he characterized as nothing but geometrical, or spatial, extension, because he thought that this was the only property of matter that was necessary to it, and therefore represented what matter truly, essentially, was. As he wrote elsewhere, "I described this matter, trying to represent it so that there is absolutely nothing, I think, which is clearer and more intelligible." The result of Descartes's "fable" was, he claimed, "a world in which there is nothing that the dullest minds cannot conceive, and which nevertheless could not be created exactly the way I have imagined it."
Excerpted from THE INTELLIGIBILITY OF NATURE by Peter Dear Copyright © 2006 by The University of Chicago. Excerpted by permission.
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List of Illustrations
Introduction: Science as Natural Philosophy, Science as Instrumentality
1. The Mechanical Universe from Galileo to Newton
2. A Place for Everything: The Classification of the World
3. The Chemical Revolution Thwarted by Atoms
4. Design and Disorder: The Origin of Species
5. Dynamical Explanation: The Aether and Victorian Machines
6. How to Understand Nature? Einstein, Bohr, and the Quantum Universe
Conclusion: Making Sense in Science