The I nfl uence of

Cartesian- Newton ian

Thought

4 · The Mech anistic View of life

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While the new physics was developing in the twentieth century, the mechanistic Cartesian world view and the principles of Newtonian physics maintained their strong influence on Western scientific think·

ing, and even today many scientists still hold to the mechanistic para·

digm, although physicists themselves have gone beyond it.

However, the new conception of the universe that has emerged from modern physics does not mean that Newtonian physics is wrong, or that quantum theory, or relativity theory, is right. Modern science has

come to realize that all scientific theories are approximations to the true nature of reality; and that each theory is valid for a certain range of phenomena. Beyond this range it no longer gives a satisfactory de·

scription of nature, and new theories have to be found to replace the old one, or, rather, to extend it by improving the approximation. Thus scientists construct a sequence of limited and approximate theories, or

" models," each more accurate than the previous one but none of them representing a complete and final account of natural phenomena.

Louis Pasteur said it beautifully: HScience advances through tentative answers to a series of more and more subtle questions which reach deeper and deeper into the essence of natural phenomena."l

The question, then, will be: How good an approximation is the Newtonian model as a basis for various sciences, and where are the limits of the Cartesian world view in those fields? In physics the mech·

anistic paradigm had to be abandoned at the level of the very small (in atomic and subatomic physics) and the level of the very large (in astra.

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TH E I N FLU ENCE OF CARTESI AN-N EWTONIAN THOUGHT

physics and cosmology). In other fields the limitations may be of differ­

ent kinds; they need not be connected with the dimensions of the phe­

nomena to be described. What we are concerned with is not so much the application of Newtonian physics to other phenomena, but rather the application of the mechanistic world view on which Newtonian physics is based. Each science will need to find out the limitations of this world view in each context.

In biology the Cartesian view of living organisms as machines, con­

structed from separate parts, still provides the dominant conceptual framework. Although Descartes' simple mechanistic biology could not be carried very far and had to be modified considerably during the subsequent three hundred years, the belief that all aspects of living or­

ganisms can be understood by reducing them to their smallest constit­

uents, and by studying the mechanisms through which these interact, lies at the very basis of most contemporary biological thinking. This passage from a current textbook on modern biology is a clear expres­

sion of the reductionist credo: "One of the acid tests of understanding an object is the ability to put it together from its component parts. Ul­

timately, molecular biologists will attempt to subject their understand­

ing of cell structure and function to this sort of test by trying to synthe­

size a cell."2

Although the reductionist approach has been extremely successful in biology, culminating in the understanding of the chemical nature of genes, the basic units of heredity, and in the unraveling of the genetic code, it nevertheless has its severe limitations. As the eminent biologist Paul Weiss has observed,

We can assert definitely . . . on the basis of strictly empirical investiga­

tions, that the sheer reversal of our prior analytic dissection of the uni­

verse by putting the pieces together again, whether in reality or just _in our minds, can yield no complete explanation of the behavior of even the most elementary living system.3

This is what most contemporary biologists find hard to admit. Carried away by the successes of the reductionist method, most notable re­

cently in the field of genetic engineering, they tend to believe that it is the only valid approach, and they have organized biological research accordingly. Students are not encouraged to develop integrative con-

THE M ECHANISTIC VI EW OF LIFE

cepts, and research institutions direct their funds almost exclusively to­

ward the solution of problems formulated within the Cartesian frame­

work. Biological phenomena that cannot be explained in reductionist terms are deemed unworthy of scientific investigation. Consequently biologists have developed very curious ways of dealing with living orga­

nisms. As the distinguished biologist and human ecologist Rene Dubos has pointed out, they usually feel most at ease when the thing they are studying is no longer living."

It is not easy to determine the precise limitations of the Cartesian approach to the study of living organisms. Most biologists, being fer­

vent reductionists, are not even interested in discussing this question, and it has taken me a long time and considerable effort to find out where the Cartesian model breaks down.5 The problems that biologists cannot solve today, apparently because of their narrow, fragmented approach, all seem to be related to the function of living systems as wholes and to their interactions with their environment. For example, the integrative action of the nervous system remains a profound mys­

tery. Although neuroscientists have been able to clarify many aspects of brain functioning, they still do not understand how neurons* work together-how they integrate themselves into the functioning of the whole system. In fact such a question is hardly ever asked. Biologists are busy dissecting the human body down to its minute components, and in doing so are gathering an impressive amount of knowledge about its cellular and molecular mechanisms, but they still do not know how we breathe, regulate our body temperature, digest, or focus our attention. They know some of the nervous circuits, but most of the integrative actions remain to be understood. The same is true of the healing of wounds, and the nature and pathways of pain also remain largely mysterious.

An extreme case of integrative activity that has fascinated scientists throughout the ages but has, so far, eluded all explanation is the phe­

nomenon of embryogenesis-the formation and development of the embryo-which involves an orderly series of processes through which cells specialize to form the different tissues and organs of the adult body. The interaction of each cell with its environment is crucial to

* Neurons are nerve cells that have the ability to receive and transmit nervous im­

pulses.

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THE I N FLUENCE OF CARTESIAN�NEWTO NIAN THOUG HT

these processes, and the whole phenomenon is a result of the integral coordinating activity of the entire organism-a process far too complex to lend itself to reductionist analysis. Thus embryogenesis is consid�

ered a highly interesting but quite unrewarding topic for biological re�

search.

The reason why most biologists are not concerned with the limita�

tions of the reductionist approach is understandable. The Cartesian method has brought spectacular progress in certain areas and con�

tinues to produce exciting results. The fact that it is inappropriate for solving other problems has left these problems neglected, if not out­

right shunned, even though the proportions of the field as a whole are thereby severely distorted.

How, then, is this situation going to change?

I

believe that the change will come through medicine. The functions of a living orga�

nism that do not lend themselves to a reductionist description-those representing the organism's integrative activities and its interactions with the environment · are precisely the functions that are crucial for the organism's health. Because Western medicine has adopted the re­

ductionist approach of modern biology, adhering to the Cartesian divi�

sion and neglecting to treat the patient as a whole person, physicians now find themselves unable to understand, or to cure, many of today's major illnesses. There is a growing awareness among them that many of the problems our medical system faces stem from the reduc�

tionist model of the human organism on which it is based. This is rec­

ognized not only by physicians but also, and even more so, by nurses and other health professionals, and by the public at large. There is al­

ready considerable pressure on physicians to go beyond the narrow, mechanistic framework of contemporary medicine and develop a broader, holistic approach to health.

Transcending the Cartesian model will amount to a major revolu­

tion in medical science, and since current medical research is closely linked to research in biology-both conceptually and in its organiza­

tion-such a revolution is bound to have a strong impact on the fur­

ther development of biology. To see where this development may lead, it is useful to review the evolution of the Cartesian model in the his­

tory of biology. Such a historical perspective also shows that the associ­

ation of biology with medicine is not something new but goes back to ancient times and has been an important factor throughout its his­

tory.6

THE MECHANISTIC VIEW OF LIFE

• • •

The two outstanding Greek physicians, Hippocrates and Galen, both contributed decisively to the biological knowledge of antiquity and remained authoritative figures for medicine and biology through­

out the Middle Ages. During the medieval era, when the Arabs be­

came the custodians of Western science and dominated all its disci­

plines, biology was again advanced by physicians, the most famous being Rhazes, Avicenna, and Averroes, all of whom were also out­

standing philosophers. During that time Arab alchemists, whose sci­

ence was traditionally associated with medicine, were the first to at­

tempt chemical analyses of living matter and, in doing so, became the precursors of modern biochemists.

The close association between biology and medicine continued through the Renaissance and into the modern era, where decisive ad­

vances in the life sciences were achieved again and again by scientists with medical backgrounds. Thus Linnaeus, the great classifier of the eighteenth century, was not only a botanist and zoologist but also a physician, and in fact botany itself developed from the study of plants with healing powers. Pasteur, though not a physician himself, laid the foundations of microbiology that were to revolutionize medical sci­

ence. Claude Bernard, the founder of modern physiology, was a physi­

cian; Matthias Schleiden and Theodor Schwann, the ori�inators of cell theory, had medical degrees, and so did Rudolf Virchow, who formu­

lated cell theory in its modern form. Lamarck had medical training, and Darwin also studied medicine, albeit with very little success.

These are just a few examples of the constant interplay between biol­

ogy and medicine which is continuing in our time, where a significant proportion of funds for biological research is provided by medical in­

stitutions. It is quite likely, therefore, that medicine and biology will once more be revolutionized together when biomedical researchers rec­

ognize the need to go beyond the Cartesian paradigm to make further progress in the understanding of health and illness.

The Cartesian model of biology has had many failures and many successes since the seventeenth century. Descartes created an uncom­

promising image of living organisms as mechanical systems and thus established a rigid conceptual framework for subsequent research in physiology, but he did not spend much time on physiological observa­

tion or experiments and left it to his followers to work out the details of the mechanistic view of life. The first to be successful in this attempt

105

TH E I N FLU ENCE OF CARTESIAN-NEWTO NIAN THOUGHT

.

was Giovanni Borelli, a student of Galileo, who managed to explain some basic aspects of muscle action in mechanistic terms. But the great triumph of seventeenth-century physiology came when William Harvey applied the mechanistic model to the phenomenon of blood circulation and solved what had been the most fundamental and diffi­

cult problem in physiology since ancient times. His treatise,

On the Movement of the Heart,

gives a lucid description of all that could be known of the blood system in terms of anatomy and hydraulics with­

out the aid of a microscope. It represents the crowning achievement of mechanistic physiology and was praised as such with great enthusiasm by Descartes himself.

Inspired by Harvey's success, the physiologists of his time tried to apply the mechanistic method to describe other bodily functions, such as digestion and metabolism, but all their attempts were dismal fail­

ures. The phenomena physiologists tried to explain-often with the help of grotesque mechanical analogies-involved chemical and elec­

trical processes that were unknown at the time and could not be de­

scribed in mechanical terms. Although chemistry did not advance very far in the seventeenth century, there was a school of thought, rooted in alchemical tradition, that tried to explain the functioning of living or­

ganisms in terms of chemical processes. The originator of this school was Paracelsus von Hohenheim, a sixteenth-century medical pioneer and extremely successful healer, half sorcerer and half scientist, and al­

together a most extraordinary figure in the history of medicine and bi­

ology. Paracelsus, who practiced his medicine as an art and an occult science based on alchemical concepts, believed that life was a chemical process and that disease was the result of an imbalance in the body chemistry. Such a view of illness was far too revolutionary for the sci­

ence of his time and had to wait several hundred years to gain broad acceptance.

In the seventeenth century physiology was divided into two oppos­

ing camps. On the one side were the followers of Parace1sus, who called themselves "iatrochemists"* and believed that physiological functions could be explained in chemical terms. On the other side were those known as "iatromechanists," who followed the Cartesian approach and held that mechanical principles were the basis of all bod-

* From the Greek iatros ("physician").

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THE M ECHANISTIC VI EW OF LIFE

ily functions. The mechanists, of course, were in the majority and con­

tinued to construct elaborate mechanical models which were often patently false but adhered to the paradigm that dominated seven­

teenth-century scientific thought.

This situation changed considerably in the eighteenth century, which saw a series of important discoveries in chemistry, including the discovery of oxygen and Antoine Lavoisier's formulation of the mod­

ern theory of combustion. The "father of modern chemistry" also demonstrated that respiration is a special form of oxidation and thus confirmed the relevance of chemical processes to the functioning of living organisms. At the end of the eighteenth century a further di­

mension was added to physiology when Luigi Galvani demonstrated that the transmission of nerve impulses was associated with an electric current. This discovery led Alessandro Volta to the study of electricity and thus became the source of two new sciences, neurophysiology and electrodynamics.

All these developments raised physiology to a new level of sophisti­

cation. The simplistic mechanical models of living organisms were abandoned, but the essence of the Cartesian idea survived. Animals were still machines, although they were much more complicated than mechanical clockworks, involving chemical and electrical phenomena.

Thus biology ceased to be Cartesian in the sense of Descartes' strictly mechanical image of living organisms, but it remained Cartesian in the wider sense of attempting to reduce all aspects of living organisms to the physical and chemical interactions of their smallest constituents.

At the same time the strict mechanistic physiology found its most forceful and elaborate expression in the polemical treatise

Man a Ma­

chine,

by La Mettrie, which remained famous well beyond the eigh­

teenth century. La Mettrie abandoned the mind-body dualism of Des­

cartes, denying that humans were essentially different from animals and comparing the human organism, including its mind, to an intri­

cate clockwork:

Does one need more . . . to prove that Man is but an Animal, or an as­

semblage of springs which all wind up one another in such a way that

one cannot say at which point of the human circle Nature has begun? . . . Indeed, I am not mistaken; the human body is a clock, but immense and constructed with such ingenuity and skill that if the wheel

107

THE I NFLUENCE OF CARTESIAN·N EWTO NIAN THOUGHT whose function it is to mark the seconds comes to a halt, that of the minutes turns and continues its course. ₇

La Mettrie's extreme materialism generated many debates and con·

troversies, some of which reached into the twentieth century. As

a

young biologist Joseph Needham wrote an essay in defense of La ^Met·

trie, published in

1928

and entitled, like

La

Mettrie's original,

Man

^a

Machine.8

Needham made it clear that for him at least at that time science was to be identified with the mechanistic Cartesian ap­

proach. "Mechanism and materialism," he wrote, "lie at the founda­

tion of scientific thought,"9 and he explicitly included the study of mental phenomena in such a science: " I by no means accept the opin­

ion that the phenomena of the mind are not amenable to physico-chemical description. All that we shall ever know of them sci ..

entifically will be mechanistic . . ." lO

Toward the end of his essay Needham summed up his position

on

the scientific view of human nature with the forceful statement: "In science, man is a machine; or if he is not, then he is nothing at all." ll Nevertheless, Needham later left the field of biology to become one of the leading historians of Chinese science and, as such, an ardent advo­

cate of the organismic world view that is the basis of Chinese thought.

It would be foolish to categorically deny Needham's claim that sci­

entists will be able, some day, to describe all biological phenomena in terms of the laws of physics and chemistry, or rather, as we would say today, in terms of biophysics and biochemistry. But this does not mean that these laws will be based on the view of living organisms as ma­

chines. To say so would be restricting science to Newtonian science.

To understand the essence of living systems, scientists whether in biophysics, biochemistry, or any other discipline concerned with the study of life _will have to abandon the reductionist belief that com­

plex organisms can be described completely, like machines, in terms of the properties and behavior of their constituents. This should be easier to do today than in the

1920S,

since the reductionist approach has had to be abandoned even in the study of inorganic matter.

In the history of the Cartesian model in the life sciences, the nine­

teenth century brought impressive new developments because of the remarkable advances in many areas of biology. The nineteenth century is best known for the establishment of the theory of evolution, but it