Association for the Foundations of Science, Language, and Cognition,

E-PANEL Discussion on Reductionism: Bialkowski's and Weinberg's texts

AFOS is organizing an e-mail debate about the problem of reductionism.


1) In Chapter 16 of the third volume of OLD AND NEW ROADS OF PHYSICS, "Is physics a universal science?", Grzegorz Bialkowski discusses in a rather informal language the question of why physics can be viewed as a fundamental scientific discipline. One can find in that part of his book various clearly stated and inspiring ideas concerning unity of science and the program of reduction of scientific theories to the more fundamental ones, eventually to physics. In a very sober way Bialkowski discusses some traps of the reductionist program, clearly defines three notions of reduction, and undertakes several other points of considerable methodological significance. Grzegorz Bialkowski was one of the eminent Polish physicists. Till his death in 1990, he was the Rector of the Warsaw University. The book whose fragment is to be discussed was published in Polish. The editors of Foundations of Science are grateful to Wiedza Powszechna the publisher of the book and the owner of its copy rights for granting them the right for translating Chapter 16 into English and using the English version for both the e-discussion and the planned publication.

2) 'Reductionism Redux' is an article that Steven Weinberg wrote about the problem of reductionism. Steven Weinberg defends the, what he calls, deep reductionism en collects arguments to show that this deep reductionist is the most important and fruitful of scientific methodologies. Steven Weinberg is Nobel Price of Physics and author of the celebrated "The First Three Minutes'. He is currently professor of physics at the university of Texas in Austin, Texas.

AIMS OF THE PANEL: To single out and to formulate in as clear way as possible those issues within the area covered by Bialkowski's and Weinberg's texts which deserve further attention and inquiry of theorist of science.

The discussion has started with reactions from several people.

Selected, carefully edited and authorised fragments of the discussion will be published (along with Bialkowski's text) in one of the next issues of FOUNDATIONS OF SCIENCES, FOS the journal of the ASSOCIATION FOR FOUNDATIONS OF SCIENCE, AFOS.

Those who are interested to participate in the debate can send their reactions to Ryszard Wojcicki, President of AFOS, at the address, or Diederik Aerts, Secretary of AFOS, at the address

Is physics a universal science?

Grzegorz Bialkowski

This text is a draft of English version of one of the last chapters (Chapter 16) of Grzegorz Bialkowski's three volume book "tare in nowe drogi fizyki" ("Old and new roads of physics" published in Polish by Wiedza Powszechna in 1985)}

Our considerations are about to conclude. Perhaps now, better than at the beginning, we are able to understand and appreciate what physics is. The time is ripe for a summary. It cannot be an inventory of achievements of this discipline, for this would require writing this book anew. I want to dwell on the role that physics plays in our cognitive system as a whole. In one of the introductory chapters of the first volume of this book, I have already mentioned expansionism, the insatiability of physics, by which from the very beginning physics entered more and more vigorously onto the domains explored by other natural sciences. The beginning of physics is the beginning of that process. Thus, the old Aristotelian physics divided the Universe onto two essentially different parts. To abolish that view, it was necessary to show the identity of laws as well as the congruity of phenomena taking place in the two fundamental parts of the Aristotelian Universe separated by the sphere of the Moon.

That was the task undertaken primarily by Mechanics. The observations of eminent and reliable Renaissance astronomers, such as Tycho de Brahe, Pavel Heinzel and Elias Camerarius allowed Kepler to formulate phenomenological laws which, in turn, open the way to the Newtonian gravitation theory. That was the first great triumph of physics and one may wonder if its essence is not the subsumption of a great part of astronomy to physics. One should not think that the "intrusion" of physics into the world of astronomy took place only in mechanics. It suffices to read in Galileo's dialogue description of (entirely earthly) experiments that serve to demonstrate to Simplicio that the Moon by no means is a polished crystal ball as was stubbornly maintained by Middle Age Aristotelians but that its surface is coarse, full of clods that disperse rather than reflect light. What a wonderful observation and proof (not to be ignored) that a mirror placed on a white coarse wall will be perceived as darker not as lighter than the wall, unless it just casts on us a sheaf of reflected light.

The principle of unity of matter explicitly formulated by Giordano Bruno, but intuitively shared by many, plays here the key role. Presenting the parts of his "Cena de le Cenari" ("The Ash Wednesday Supper") Bruno wrote:

Thus, according to Bruno, there are no such two different elements as "earthness" and "heavenness" but all over the universe the matter is the same. Only the discoveries of Fraunhofer, Kirchoff and others, who were able to demonstrate that the atmosphere of the Sun (as well as other stars) contain the same elements as those present on Earth, provided full observational confirmation of Bruno's cosmological principle. Bruno himself had almost no evidential support for his principle. Rightly then, still in the nineteenth century, Comte could maintain that the chemical composition of heavenly bodies will remain for humans an enigma forever. Rightly, because at that time there were no signs of any possibility whatsoever to approach that problem and the mind set of positivists did not go far beyond the facts then available. But, at the same time, this demonstrates the narrowness of positivism. As Weinberg has pointed out in his beautiful book "The first three minutes" the fully objectivist approach may not be the best receipe for developments of science. It may pay to ignore doubts and follow the conclusions from once accepted premises, regardless of where they lead us.

On the other hand, observations of the spectra of stars and star clouds contributed to the development of physics by providing it with new experimental data. One of them was the discovery of helium with the help of spectroscopy, first in the photosphere of the Sun and only later on Earth (that explains the origin of the term "helium" -a Sun element). Throughout the last centuries and decades it has become more and more obvious that the universe is a physical laboratory of sorts. The phases of matter one may discover in the Cosmos may not be easy to produce on Earth. Besides, the very scale of the phenomena taking place in the Cosmos allows us to observe how they are influenced by the gravitational field, whose role can be rightly appreciated in those circumstances. Surely, only someone who knows the secrets of "métier", who is acquainted with the right experimental techniques, is able to reach information from that laboratory, to formulate reliable interrelations and to interpret them in a correct way. The same is true in nuclear physics or in the physics of rigid bodies; also their development requires the right methodology. Astronomy has become physics of cosmic entities. Thus, the universality of physical laws indeed extends to the whole universe.

In order to acknowledge the unity of the universe, one has had to learn the laws that govern large scale natural phenomena taking place on our glob in its atmosphere, hydrosphere and lithosphere. One could not forever trust to Zeus the responsibility for tempests, Poseidon for sea currents and Hades for volcanoes. The investigations started at a time difficult to reconstruct. When William Gilbert published his treatise on magnets, part of his concern was the Earth's magnetism already known for a for long time. Soon, Benjamin Franklin explained the nature of tempests. Since that time several centuries have passed and somebody, who reads about either an unexpected earthquake or tornado or -- on a less dramatic scale -- one who is disappointed that the weather forecast has turned out to be wrong once more, may not realize how great a progress was made in learning those phenomena and how complex they are. Our inability to forecast geophysical phenomena is caused by numerous factors; in the first place our poor knowledge of such processes as the formation of clouds or the influence of the state of the ionosphere on atmospheric phenomena etc. On the other hand, we do not have a sufficiently precise data base system on both the present and past geophysical events on the global scale, which is partially due to our incomplete knowledge of the origin and evolution of our planet. Thirdly, at last, one may be afraid that if one were able to make use of both the relevant general laws and the necessary information about the initial and boundary conditions (such as e.g. the activity of the Sun and the intensity and composition of cosmic radiation) it would turn out that the resulting system of equations is extremely complicated. It will not be easy to tell from all the factors it includes, those which are more and which are less important. What is worse, the actual course of events may possibly depend on some allegedly inessential disturbing factors (e.g. the shape of the seashore line, an eruption of a volcano or a huge forest fire). Instability of solutions caused by small, on average inessential, disturbances which nevertheless affect the concrete singular course of events may result in ruling out any possibility of any forecasts other than statistical. But that was a digression. One way or another, nobody doubts that the only way to learn the large scale processes characteristic of our planet is to apply the laws of physics to our environment which is still unknown even though it is so close to us.

The advance of electrodynamics, and especially quantum mechanics has opened entirely new perspectives for physics. I have already mentioned, that the progress of physics has allowed us to understand many phenomena and techniques of fundamental significance for chemistry such as electrolytic dissociation, diffusion, transformation of phases of matter, or the structure of molecules. Still, the basic achievement is accounting for the nature of valence and chemical binding. At present, the theory of the hydrogen molecule is so advanced that there is no doubt that we understand this quantum system quite well. And, apart from some specific methods of calculations, what makes it possible are in principle only Coulomb's law, Schrödinger's equation and Pauli's exclusion principle. Of course, the greater the number of bodies that participate in a specific phenomenon the more complex is the task of accounting for that phenomenon. Thus for instance the properties of lithium are more intelligible than those of lead or californium. For the same reason we understand the molecule of hydrogen better than that of water and the latter better than the protein molecule of any specific kind. However, one should not expect to discover in chemistry, at least not in its foundational part, any laws characteristic for this discipline only, all these laws are derivable from the basic properties of matter. In principle, the laws of physics suffice to explain the structure of chemical substances and the kinetics of chemical reactions, even though, in practice, we may not be able to derive that structure from the basic laws. However, nobody seeks to explains the motion of water running from an outlet by resorting to the general laws of hydrodynamics and still nobody doubts, that these laws account for the characteristic of that motion.

Going towards still more complicated structures, we encounter living creatures and their parts. This area is covered by biological investigations. The role of physics has considerably increased also here. The relevance of physics for the traditional biological disciplines of descriptive and taxonomic nature is small. Physics can say a little about ecological problems either. But the domains formed more recently, genetics in the first place and, to a fairly large extent, also physiology are more and more penetrated by physics. Indirectly, that results in its growing significance for medicine and psychology, regardless of whether the psychological issues are approached by examining physiological phenomena underlying human psyche or in the way typical for be- haviorism.

One may ask what are both the general reasons and symptoms of that expansion of physics. I see several.

To begin with, physics supplies all the other natural sciences with both the most general and the most basic laws of nature, thus serving as their foundations. One cannot imagine any theory of living organisms without thermodynamic, theory of vision without both optics and knowledge about absorption of light by matter. One cannot imagine accounting for the processes of polymerization without knowledge of intermolecular forces. With qualifications defined by physics itself, those basic and general laws of physics are valid always and all over.

Another reason for the growing significance of physics for the natural sciences is undoubtedly the fact that it serves as an attractive methodological pattern. Throughout the short period of its "scientific stage", physics has made progress so huge and so unquestioned that it is only natural to conjecture that this success may somehow be linked to the method of inquiry adopted in physics. This method consists in: a combination of atomistic analysis with the empiricist resort to reality, a presentation of these results in quantified form, and, finally, rational argumentation and generalizations. The quantitative nature of physics is especially appealing to ones imagination and it is most often adopted in other branches of science. In a way more or less cognizant and more or less justified by both the nature and the achieved stage of a given discipline, the natural sciences seek to follow the pattern of physics.

The above leads to the third reason for proliferation of physics to other disciplines, but seemingly more 'technical' and less important than the others. In their search for quantitative laws, natural sciences must resort to measurement. But all the measuring instruments are operating on the base of physical laws and measure physical quantities. The number, the outcome of measurement, not just that of counting elements (say all the animals within a certain region), is in natural science a physical quantity. Still, quite understandably, for the researcher in specific natural discipline other than physics, it is not a physical quantity that is measured. Rather, the quantity in questions is merely a measure of a phenomenon characteristic of his own discipline. Nevertheless, if, say, one applies an encephalogram to examine the electric activity of the brain, one actually measures some physical magnitude. If one carries out the spectral analysis of a sample in order to learn its chemical composition one again measures some physical quantity. One may say that for natural sciences physics is a gateway to the world of quantitative laws.

There is an important consequence of the above fact. Since every measurement is a measurement of a physical quantity, that quantity becomes a factor of quantitative analyses, and consequently, as one may expect, results in tendency to translate terms characteristic of specific natural sciences into the language of physics. This language is the language one must apply when one executes measurements. Obviously, it would be a mistake to think that since there is such a translation the phenomena explored by a given discipline entirely reduce to physical ones. One should not confuse semantic and ontological issues. Nevertheless, the temptation toward identifying the examined phenomena with some physical ones will surely manifest itself, if not otherwise then as a tendency toward revealing complementarity of cognition in the relevant disciplines. It is difficult to say what might be the final outcome of that process.

Does physics have any chance to become a universal science in which all the other natural disciplines will dissolve? Such a program of physicalisation and reductionism has its own partisans and representatives, but it also has its declared enemies. It was advocated in a very strong way by the representatives of neopositivism who promoted the idea of "unified science". But on this issue, I believe, one should preserve a sober skepticism.

It is worth dwelling for a while on what it means to reduce one scientific discipline to another. The ambiguity of the idea may result in confusion. One of the possible explications is the following. Imagine two sciences wirology and femology. The latter can be reduced to the former, if, firstly, all its terms can be uniquely assigned to some terms of wirology. and, secondly, the laws of femology translated in this well defined way become laws of wirology. If this is the case, one is entitled to say that femology is a branch of wirology, even though, for some historical and perhaps accidental reasons it has been stated in a separate language. If one does not want to go that far, one may maintain that femology provides wirology with a specific interpretation of some of its laws which may happen to be useful.

This is how geometry and algebra are linked. After the invention by Descartes of the analytic method, the notions and the laws of geometry became notions and laws of algebra. For instance, instead of using the notion of a circle one may use the equation of a circle; a point becomes an ordered set of three numbers (or n numbers in a n-dimensional space). The reader is surely aware that such links between different branches of science are not what we are interested in. Reduction of the kind we have discussed is lacking in something essential, namely in accounting for the properties of the whole by the properties of its constituents. It can be called logical reduction, and we have in mind one that can be called atomistic.

Let me start with a commonplace. Any whole, unless it is a set of elements independent from one another (actually, to some extent also in this case), has some properties which are not those of its components. The stronger the dynamical constraints among the elements the more distinct are the properties of the whole they form. About no molecule of water can one say that it is liquid, about no atom of oxygen and no atom of hydrogen combined in a molecule can one say that they have an electric dipole moment, about no electron or proton of an atom can one say that they are electrically neutral and that their dimension is of order 10-10m. Actually, the fact that combining parts into a whole always results in the emergence of some new properties is known from everyday experience and does not need appeal to the laws of the microworld. But what does it mean to explain the properties of a whole by the properties of its parts?

Let us consider a very simple example: an atom of hydrogen. The lightest atom of hydrogen has a single proton as its nucleus, while the nuclei of heavy hydrogen, deuterium, consist of one proton and one neutron. In order to form a theory of the hydrogen atom we have to know the relevant general laws of physics, in this case those of quantum mechanics. This will not suffice, however. One has to specify which isotope of hydrogen is to be examined, for the pattern of the energy spectrum depends on the mass of the nucleus, on its spin, magnetic momentum and on other properties. In other words the theory of the hydrogen atom presupposes familiarity with both general laws of physics and properties of parts of the atom. One may also state this claim in somewhat converted form as follows. In order to determine the properties of the whole one has to know not only the properties of its parts but also the general laws of physics which are independent of those properties. The same applies to a molecule of hydrogen. Besides the relevant properties of singular atoms, we have to know laws of physics in order to know that the molecule will perform some rotations in space and some oscillations along the axis linking the two atoms. The physical laws in question do not apply to single atoms! In general, the course of a phenomenon is not determined by physical laws only or by the "fabric data" only. In many cases the situation is still more complex, for an essential role can be played by either the initial conditions or even the whole history of the system (the history is essential already for phenomena such as ferromagnetism). This role can also be played by the boundary conditions which determine the behavior of the system in its environment. For instance, in order to form a theory of the hydrogen atom, if we want the atom to be stable, we must request that its electron is not able to separate to unlimited distance unless it is supplied with additional energy not lower than the energy of ionization.

We are now approaching the gist of the matter. The presently known laws of physics do not determine all those conditions in which they are applied. For instance, neither the value of mass nor that of charge of an electron follow from the law of physics. Perhaps -- in accordance with Mach's principle -- if the number of protons (more generally if the distribution of mass) were different, the electron's mass would also be different. The key question is then whether and to what extent the laws of physics determine the universe consistent with them. Is the universe in which we live the only possible universe? Would it be possible, preserving the laws of the universe, to change, if not arbitrarily then almost arbitrarily, the data concerning the fabric of a system, and its initial and boundary conditions. Today we cannot answer these questions.

The situation then is as follows. One can say about femology that it is reducible to wirology in the atomistic sense of the word if (a) the laws of wirology suffice to fully account for the properties of the elements of femological systems, (b) by resorting to the laws of wirology one is able to account for the behavior of femological systems sufficiently well. Thus, whatever is specific for femology becomes stated as a class of conditions that tell us how laws of wirology should be applied. The atomistic reduction would have a chance to be tantamount to logistic reduction only if our universe, ruled by the laws of wirology, were the only possible universe.

Let us ask then whether there is any chance to prove feasibility of the doctrine of atomistic reduction for natural science as a whole. I am afraid, that task encounters two obstacles.

The first one is perhaps purely technical. The complexity of systems one has to examine when one moves from physics to chemistry is so great that it is practically impossible to perform the calculations which could render the ultimate proof of reducibility of chemical phenomena to physical ones. This state of affairs, even more acute in the case of biology, have forced the two disciplines to invent various phenomenological models which describe phenomena they examine in a sufficiently adequate way, but without reducing them to any elementary events. It does not mean that those models can never be stated in physical terms -- that may happen -- but if it does mean, the models may still be detached from the prime principles of physics. For instance, I can imagine that someday the behavior of a cell will be described by an equation stated in terms of thermodynamic, electrodynamics and mechanics in a way consistent with the theory of chemical transformations. However, I hardly can imagine that such an equation can be derived from the basic physical laws.

In this way, we arrive at a type of reduction of a somewhat less restrictive kind which can be called semantic. In this case femology has its own laws whose reduction to atomistic laws of wirology remains an open question but the laws of femology can be fully for- mulated in the language of wirology. If so, the relation of femology to wirology would resemble that of an island to the continent which are not linked (perhaps temporarily only) by any isthmus.

Most likely, however, even a reduction of the above kind will not always be possible. In order to meet any doubt, let me discuss an example drawn from physics. As I have already noticed in chapter 11 of vol. 1, one of the still open problems is the derivation of the laws of behavior of complexes formed from many molecules (atoms) from the laws of behavior of atoms. In other words, the problem that remains open is that of basing statistical physics on mechanics. Still we know how to translate thermodynamical terms into mechanical terms. For instance, as was proved, temperature corresponds to the average kinetic energy of the molecule. This fact is fairly recent, for it was established about 130 years ago. Could one imagine that thermodynamics was part of physics before it was discovered? The answer must be 'yes'. But why? I believe this for two reasons. Firstly, up to some technical details, the methodology of thermodynamical investigations was the same as that of mechanics: measurements, equations, atomistic reasoning ( in thermodynamics one can examine and one does examine the properties of systems by examining the properties of subsystems), etc. Secondly, it was commonly taken for granted that there were no thermodynamical phenomena which could not be examined without going beyond standard physical methodology. True, the theory of caloric was a very special physical theory, but the researchers dealing with it could and should apply the same methods as were applied in other domains of physics. Thus, reduction of perhaps a less restrictive kind is methodological reduction, the one which take place when it turns out that femological investigations can be carried out by appealing to exactly the same methodology as applied in wirology.

I guess that various misconceptions of reductionism may result either from confusing various notions of reduction or from the view that the hierarchy of those notions serves merely to indicate the direction of successive transformations in science which must lead from lower to higher forms of reduction , i.e. from methodological via semantic and logical up to atomistic. But such transformations need not exist.

There is another difficulty I can see, perhaps hypothetical only, which may impede the reductionist program. In order to make my view easier to follow, I shall use a fairly realistic example. For students of the structure of the atomic nucleus, the deuteron -- a two nucleons system -- has been a paradigmatic case. Since there were thousands of papers on deuterium published, it is reasonable to believe that the deuteron structure is well known. That structure can be explained by admitting forces of a special kind acting between the two nucleons. It seems evident that the knowledge of the interactions between the two nucleons can be expanded to the case of three nucleons. There are two nuclei consisting of three nucleons: tritium, i.e. H31 and He32. Unfortunately, physics has not been able to develop a conclusive theory of these nuclei. One of the reasons has been insufficient knowledge about the forces acting in such systems. One does not know whether forces acting among the three components of those nuclei are tantamount to the forces acting between all the three pairs of nucleons (the nucleons A and B, B and C, and C and A)? Or perhaps there are some additional forces which engage all three particles A, B and C at the same time? The point is that one cannot learn 3 body forces by analyzing two-nucleon systems; even our excellent knowledge of the deuteron is irrelevant here, because those forces -- if any -- have no chance to manifest themselves in such a system.

One may suggest a still simpler, though less 'clean' example. If one examines the deuteron from the point of view of its inner construction, one is able to see only nuclear forces. In that case the proton's charge is irrelevant, even though one knows that in a system such as an atom of deuterium the proton can be active electromagnetically. But to demonstrate that, one must make the system more complex.

Looking at the things from a somewhat more general perspective, we see that it is conceivable that some tiny elements of matter are capable of interactions which may take place if and only if those elements become constituents of a sufficiently complex structure. Please note, that this is no 'revitalization of vitalism'; no rejection of atomistic, or even semantic reduction is intended. The potential abilities in question are supposed to be part of the characteristic of elements of matter and it suffices to combine those elements (which, in principle, should be feasible) in order for those properties to automatically reveal themselves. Since our investigations of simpler structure do not allow us to learn anything about those abilities, our dealing with more complex structures results in discovering some qualities characteristic of the latter that are neither present nor reducible to the qualities of simpler structures. Personally, I do not think that anything in chemistry or biology suggests that we chance to encounter the above situation. Still I have mentioned that perhaps only theoretical possibility because it should certainly not be ignored.

I would summarize the situation as follows. Attractive as it is for the uniformity of its vision, the program of physicalization of natural sciences may not be, and most likely will never be, feasible. It will not be feasible for technical but presumably (with various question marks) also substantial reasons. If so, the significance of physics for other natural sciences will keep growing but the latter will never completely loose their independence.

A separate issue is the relation between physics and the social sciences and humanities. It seems to me that the differences between these two kind of scientific investigations are rather essential. Needless to say, like physics, also human and social sciences seek to learn facts in a reliable way. The facts are than separated, and one looks for the most significant among them, singles them out and leaves the remaining ones aside. Taking into account the facts of special significance, one looks for regularities which account, at least in a rough way, for the examined processes and their outcomes. Going deeper into the structure of non-natural sciences we notice various new elements. To begin with, one becomes struck by the multiparametricity of phenomena (which is considerably greater than even in geophysics). The number of variables which "a priori" are to be taken into account is enormous. The characteristics of soil and climate, of the hydrological system, demographic and economical factors, the endowment (of both biological and social nature) of the inhabitants occupying the examined region, the relevance of tradition and of socially accepted systems of values, such evasive factors as the sense of social discipline included, and finally the capaci- ties and achievements of eminent promoters of both culture and history of the community, supplemented perhaps by some elements of their individual biographies... Which of all of these variables deserve to be focused upon and taken into account? Which should be the criteria applied for deciding the question? In natural sciences we know how to settle this issue. We examine many copies of the same system, change the variable which we suspect to be of greater significance than the others and observe the outcome. But this is possible neither in social nor in human sciences. They, especially the latter, deal with unique systems with no copies available. There was only one Adam Mickiewicz, only one Poland, and as we are more and more inclined to believe, only one human civilization. So, we cannot as easily experiment with them as with the objects examined by natural sciences. But suppose, we can do that. Then, it will turn out that there are some other features which make social sciences and humanities different from natural science. There is no doubt that social consciousness is one of factors that determines social behavior. On the other hand social and human sciences are part of that consciousness. In other words those sciences are kind of social introspection. But reliability of introspection as a research method of psychology is questioned. One argues that one cannot be aware of a process taking place in one's mind without affecting it. For similar reason social sciences can be a source of self-confirming hypotheses and forecasts.

The unique character of a phenomenon does not exclude a statistical approach. For instance, each family is different from any other. Still, one may estimate how many families have such and such income, how many of them end in divorce, etc. Obviously, investigations of that kind are of considerable significance. Quite often, however, it is not a statistical regularity but a specific singular course of events which matters for us. Geophysics is able to tell the average temperature in July, but when planning my vacations I want to know the July temperature in a more exact way. A sociologist may tell me that, say, 10% of marriages end in divorce every year, but I may want to know the chances of divorce of my own marriage within the next ten years. Statistics smoothes out all the inputs from 'accidental' factors whose appearance result in in- stability of individual events. But we are often concerned with exactly those individual events for they matter for us especially.

Finally, here in the last and perhaps the most important point. The world of social sciences and humanities is the human world and the human world is the world of values. In natural sciences values, even economical, are left aside. The only value sought to be imple- mented is epistemic value, that is truth. On the other hand, in social sciences the role of values is enormous. Even the issues to be examined depends on the accepted systems of values. That explains why, Mickiewicz has attracted many more studies than other poets considered to be of secondary significance. Also, this fact directly affects the process of investigations, the researcher is forced to accommodate himself to the socially accepted hierarchy of values in the community to which (s)he belongs.

Obviously, one may try to apply the reductionist approach to a value system and seek to explain it by biological factors. The deepest one (even though unpleasant) attempt of the kind is sociobiology. The proponents of this approach claim that the behavior of all the organisms, and the social interdependencies among them are completely determined by their (one may say -- blind) will of survival and reproduction. There are several things, partially related to our previous discussion on reductionism, which are to be said on this topic. It seems entirely obvious that the genetic material alone does not fully determine the fate and the development of an organism. The crop from a properly fertilized lot will be larger than that from a lot left idle. The 'gene mechanics' must then take into account all the relevant biological matter as well as initial and boundary conditions. And, what are those conditions in the case of humans? Presumably we all agree that for each person, one of the most important factors are the person's past history, the environment in which (s)he both have been raised and is being raised (for this process never ends) and eventually the stage of the person's consciousness, moral consciousness in particular, determined by those factors. Is there any room left for free will? How to act is quite a different question. But the elements of consciousness of both private needs and socially accepted rules of behavior should necessarily be taken into account as part of those conditions which are relevant for the behavior of a given person. On many occasions, genetic considerations determine only the likelihood of the appearance of a specific trait in the phenotype. If even the size of people is not fully determined genetically (for if it were otherwise, we would not be able to understand why from generation to generation people are taller), then, to even a larger degree, this applies to intellectual faculties of humans and their systems of beliefs.

Incidentally, the idea to explain human behavior in purely biological terms (even though its fruitfulness is beyond any doubt) leaves many questions unanswered. The most important one is why (since the genetic material of humans is essen- tially the same throughout many centuries) the patterns of both behavior and of life evolve within the same or even shorter spans of time so quickly. One may suspect that sociobiology is of a scientific nature only to some extent, being at the same time a certain research program and a certain ideology.

Since, as one may guess, any road from physics to the human world must lead through biology, and the conjecture that biology will eventually be able to account for social phenomena seems to be very unlikely, one should be that much skeptical of the role of physics in this context. The process of physicalisation will stop at that juncture where physiology of the brain and that of the neurological system changes into psychology.


Steven Weinberg

  edited by John Cornwell,
  introduction by Freeman Dyson,
  Oxford University Press,
  212 pp., 23.00USD

It used to be traditional for college courses on the history of philosophy to begin around 600 BC with Thales of Miletus. According to later writers, Thales taught that everything is made of water. Learning about Thales, undergraduates had the healthy experience of starting their study of philosophy with a doctrine that they knew to be false.

Though wrong. Thales and his pre-Socratic successors were not just being silly. They had somehow come upon the idea that it might be possible to explain a great many complicated things on the basis of some simple and universal principle - everything is made of water, or everything is made of atoms, or everything is in flux, or nothing ever changes, or whatever. Not much progress could be made with such purely qualitative ideas. Over two thousand years later Isaac Newton at last proposed mathematical laws of motion and gravitation, with which he could explain the motion of the planets, tides, and falling apples. Then in the " Opticks ", he predicted that light and chemistry would someday be understood " by the same kind of reasoning as for mechanical principles", applied to " the smallest particles of nature".

By the end of the nineteenth century physicists and chemists had succeeded in explaining much of what was known about chemistry and heat, on the basis of certain assumed properties of some ninety types of atoms - hydrogen atoms, carbon atoms, iron atoms, and so on. In the 1920s physicists began to be able to explain the properties of atoms and other things like radioactivity and light, using a new universal theory known as quantum mechanics. The fundamental entities to which this theory was applied were no longer the atoms themselves but particles even more elementary than atoms - electrons, protons, and a few others - together with fields of force that surround them , like the familiar fields that surround magnets or electric charges.

By the mid-1970s it had become clear that the properties of these particles and all other known particles could be understood as mathematical consequences of a fairly simple quantum theory, known as the "standard model ". The fundamental equations of the standard model do not deal with particles and fields, but with fields of force alone; particles are just bundles of field energy. From Newton's time to our own we have seen a steady expansion of the range of phenomena that we know how to explain, and a steady improvement in the simplicity and universality of the theories used in these explanations.

Science in this style is properly called reductionist. In a recent article in these pages (1) Freeman Dyson described reductionism in physics as the effort "to reduce the world of physical phenomena to a finite set of fundamental equations". I might quibble over whether it is equations or principles that are being sought, but it seems to me that in this description Dyson has caught the essence of reductionism pretty well. He also cite the work of Schroedinger and Dirac on quantum mechanics in 1925 and 1927 as "triumphs of reductionism. Bewildering complexities of chemistry and physics were reduced to two lines of algebraic symbols".

You might have thought that these illustrious precedents would inspire a general feeling of enthusiasm about the reductionist style of scientific research. Far from it. Many science kibitzers and some scientists today speak of reductionism with a sneer, like postmodernists talking about modernism or historians about Whig historiography. In 1992 John Cornwell, the director of a project at Jesus College, Cambridge, on the sociology of science, convened a group of well-known scientists and philosophers to meet there to discuss reductionism. It was at this symposium that Dyson gave the talk on which his eloquent NEW YORK REVIEW article was based. The collected papers of this symposium, NATURE'S IMAGINATION(2), contains articles with titles such as "Must mathematical physics be reductionist?" (Roger Penrose), "Reductive megalomania" (Mary Midgley), and "Memory and the individual soul: against silly reductionism" (Gerald Edelman). A review of this book by the mathematician John Casti, in NATURE, calls these the "good guys in the white hats" as opposed to the unreconstructed reductionists at the meeting like the chemist Peter Atkins and the astronomer John Barrow.

Casti is a fellow of the Santa Fe Institute, a haven for non-reductionist science. Dyson himself remarks that he has a "low opinion" of reductionism. (Coming from Dyson, this really hurts. He played a major role in the development of quantum field theory, which has been the basis of the reduction of all of elementary particle physics to the standard model.) What has gone wrong? How has one of the great themes in intellectual history become so disreputable?

One of the problems is a confusion about what reductionism is. We ought first of all to distinguish between what (to borrow the language of criminal law) I like to call grand and petty reductionism. Grand reductionism is what I have been talking about so far - the view that all of nature is the way it is (with certain qualifications about initial conditions and historical accidents) because of simple universal laws, to which all other scientific laws may in some sense be reduced. Petty reductionism is the much less interesting doctrine that things behave the way they do because of the properties of their constituents: for instance, a diamond is hard because the carbon atoms of which it is composed can fit together neatly. Grand and petty reductionism(3) are often confused because much of the reductive progress in science has been in answering questions about what things are made of, but the one is very different from the other.

Petty reductionism is not worth a fierce defense. Sometimes things can be explained by studying their constituents - sometimes not. When Einstein explained Newton's theories of motion and gravitation, he was not committing petty reductionism. His explanation was not based on some theory about the constituents of anything, but rather on a new physical principle, the general principle of relativity, which is embodied in his theory of curved spacetime. In fact, petty reductionism in physics has probably run its course. Just as it doesn't make sense to talk about the hardness or temperature or intelligence of individual "elementary" particles, it is also not possible to give a precise meaning to statements about particles being composed of other particles. We do speak loosely of a proton as being composed of three quarks, but if you look very closely at a quark you will find it surrounded with a cloud of quarks and antiquarks and other particles, occasionally bound into protons; so at least for a brief moment we could say that the quark is made of protons. It is grand reductionism rather than petty reductionism that continues to be worth arguing about.

Then there is another distinction, one that almost no one mentions, between reductionism as a program for scientific research and reductionism as a view of nature. For instance, the reductionist view emphasizes that the weather behaves the way it does because of the general principles of aerodynamics, radiation flow, and so on (as well as historical accidents like the size and orbit of the earth), but in order to predict the weather tomorrow it may be more useful to think about cold fronts and thunderstorms. Reductionism may or may not be a good guide for a program of weather forecasting, but it provides the necessary insight that there are not autonomous laws of weather that are logically independent of the principles of physics. Whether or ot it helps the meteorologist to keep it in mind, cold fronts are the way they are because of the properties of air and water vapor and so on which in turn are the way they are because of the principles of chemistry and physics. We don't know the final laws of nature, but we know that they are not expressed in terms of cold fronts or thunderstorms.

One can illustrate the reductionist world view by imagining all the principles of science as being dots on a huge chart, with arrows flowing into each principle from all the other principles by which it is explained. The lesson of history is that these arrows do not form separate disconnected clumps, representing science that are logically independent, and they do not wander aimlessly. Rather, they are all connected, and if followed backward they all seem to branch outward from a common source, an ultimate law of nature that Dyson calls "a finite set of fundamental equations". We say that one concept is at a higher level or a deeper level then another if it is governed by principles that are further from or closer to this common source. Thus the reductionist regards the general theories governing air and water and radiation as being at a deeper level than theories about cold fronts or thunderstorms, not in the sense that they are more useful, but only in the sense that the latter can in principle be understood as mathematical consequences of the former. The reductionist program of physics is the search for the common source of all explanations.

As far as I can tell, Dyson's objections are entirely directed at reductionism as a research program rather than as a world view. He regrets that Einstein and (in later life) Oppenheimer were not interested in something as exciting as black holes, and blames this on their belief that "the only problem worthy of the attention of a serious theoretical physicists was the discovery of the fundamental equation of physics". This is pretty mild criticism. Dyson does not question the value of the discovery of the fundamental equations (how could he), but only tells us that there are other things in physics to think about, like black holes. This is like a prohibitionist who is against gin because, good as it is , it distracts people from orange juice. And I am not sure that Dyson is even entirely right about Einstein and Oppenheimer as examples of the danger of the appeal of reductionism.

I recall as a Princeton graduate student going to seminars at the Institute for Advanced Study, where Dyson was a professor and Oppenheimer the director. I

Oppenheimer always sat in front and carried on a detailed technical dialogue with the speaker, whatever the topic might be. He certainly seemed interested in everything what was going on on physics, not just at the reductive forefront. In fact, even in the 1920s and 1930s, when he was doing his best research, Oppenheimer's work had much less to do with finding fundamental equations than with calculating the consequences of existing theories. By the time I met him, Oppenheimer's own research had pretty well ended, and I can believe that he explained this even to himself in the way that is cited by Dyson; but I suspect that the truth is that he had just become too famous and too busy to have time for research.

Einstein is another story. He had never immersed himself the way Oppenheimer did in the physics research of others. The physicist-historian Gerald Holton showed some years ago that Einstein was not significantly influenced by the specific experimental results of Michelson and Morley that is often described as the crucial clue that led to special relativity. I think that Einstein objected to black holes not because he found them uninteresting but rather for precisely the reason that I and many others find them interesting; they suggested an incompleteness in his beloved general theory of relativity. Physics in the reductive style had served Einstein magnificently well until the 1920s, and he was not so much wrong in trying to continue in this vein as he was in assuming that the appropriate subjects for fundamental research would continue to be what they had been in his youth: gravitation and electromagnetism. He became narrow, endlessly pursuing the false goal of unifying gravitation and electromagnetism, and cut off from exciting work on cosmic rays and elementary particles and quantum field theory that eventually led to the unification of the standard model. His real mistake is one we all risk: he became old.

Much of the criticism of reductionism is really only criticism of reductionism as a program for research. A good example is an argument by the moral philosopher Mary Midgley. In her article in the collection based on the Jesus College symposium, she asks " What, for instance, about a factual statement like 'George was allowed home from prison at last on Sunday'? How will the language of physics convey the meaning of 'Sunday'? or 'home' or 'allowed' or 'prison'? or 'at last'? or even 'George'?" This criticism would strike home if there were physicists who were trying to use physics for such a purpose, but I don't know of any.

It is not just that (as enphasized in this symposium by Atkins and the philosophers Paul and Patricia Churchland ) prison and people and thunderstorms are too complicated for us to be able to predict their behavior by following the motion of the elementary particles of which they are composed. It is also a matter of what interests us. The buzzword here is "emergence". As we deal with more and more complicated systems, we see phenomena emerge from them that are much more interesting than a mountain of computer printout describing the motion of each particle in the system ever could be. Mind is a phenomenon that emerges from the biology of complicated anomalies, just as life is a phenomenon that emerges from the chemistry of complicated molecules. We are interested in whether George is happy to be out of jail in a way that is different from our interest in his nerve cells, and we are interested in his nerve cells in a way that is different from our interest in the electrons and protons and neutrons of which they are composed. But phenomena like mind and life do emerge. The rules they obey are not independent truths, but follow from scientific principles at a deeper level; apart from historical accidents that by definition cannot be explained, the nervous systems of George and his friends have evolved to what they are entirely because of the principles of macroscopic physics and chemistry, which in turn are what they are entirely because of principles of standard model of elementary particles.

It is not so much that the reductionist world view helps us to understand George himself as that it rules out other sorts of understanding. Every field of science operates by formulating and testing generalizations that are sometimes dignified by being called principles or laws. The library of the University of Texas has thirty-fife books with the title "Principles of Chemistry" and eighteen books with the title "Principles of Psychology". But there are no principles of chemistry that simply stand on their own, without needing to be explained reductively from the properties of electrons and atomic nuclei, and in the same way there are no principles of psychology that are free-standing, in the sense that they do not need ultimately to be understood through the study of the human brain, which in turn must ultimately be understood on the basis on physics and chemistry. Henry Bergson and Darth Vader notwithstanding, there is no life force. This is invaluable negative perspective that is provided by reductionism.

I suppose Midgley might retort that she doesn't know any anti-reductionist philosophers who think that there are free-standing principles of psychology. Maybe not, though many of our fellow citizens still think that George behaves the way he does because he has a soul that is governed by laws quite unrelated to those that govern particles or thunderstorms. But let that pass. In fact, I suspect that Midgley shares the world view of grand reductionism, but holds it "not honesty to have it thus set down".

At any rate, Midgley has to reach in some peculiar directions in her search for horrible examples of reductionism. One of her targets is B.F.Skinner, the late arch-behaviorist and master pigeon trainer. I share her dislike of Skinner's refusal to deal with consciousness in his work. But why does she quote him in a critique of reductionism? I am not aware that Skinner thought very much about science like evolutionary biology or neurology which might provide reductive explanations for principles of psychology. I always thought that Skinner's problem was not reductionism, but positivism, the doctrine that science should concern itself only with what can be directly observed, like behavior. Positivism generally leads away from reductionism; for instance, at the beginning of this century it led the influential Viennese physicist-philosopher Ernst Mach to reject the idea of atoms, because they could not be directly observed.

Perhaps I do know why Midgley chose Skinner as a reductionist villain. Skinner excluded consciousness from his view of the mind, and consciousness poses the greatest challenge to reductionism. It is difficult to see how the ordinary methods of science can be applied to consciousness, because it is the one thing we know about directly, not through the senses. Peter Atkins gave a splendid in-your-face reductionist polemic at Jesus College which I thoroughly enjoyed reading. "Scientists, with their implicit trust in reductionism, are privileged to be at the summit of knowledge, and to see further into truth than any of their contemporaries". Give 'em hell, Peter! But it seems to me that Atkins is not sufficiently sensitive to the problems surrounding consciousness. I don't see how anyone but George will ever know how it feels to be George. On the other hand, I can readily believe that at least in principle we will one day be able to explain all of George's behavior reductively, including what he says about how he feels, and that consciousness will be one of the emergent higher-level concepts appearing in this explanation.

In their articles in the symposium report the neuroscientists Gerald Edelman and Oliver Sacks make what I think is too much of the supposed antireductionist implications of new ideas about the brain. In his article written with Giulio Tononi, Edelman describes his "Theory of Neuronal Group Selection", according to which the brain doesn't operate according to a preset program, but rather to one that evolves through a sort of natural selection during the life of the organism. He then argues in another article in this collection that "the kind of reductionism that doomed the thinkers of the Enlightenment is confused by evidence that has emerged both from modern neuroscience and from modern physics. I have argued that a person is not explainable in molecular, field-theoretical, or physiological terms alone. To reduce a theory of individual's behavior to a theory of molecular interactions is simply silly.... Even given the success of reductionism in physics, chemistry, and molecular biology, it nonetheless becomes silly reductionism when it is applied exclusively to the matter of the mind".

Edelman is a very distinguished scientist, and his "neural Darwinism" may well be a great advance in the theory of the mind; but when he discusses the basis of a scientific world view, I don't see what is the big difference between natural selection over millions of years producing a mental operating system that is fixed at birth or natural selection proceeding over millions of years and then continuing for a few decades after birth. Neural Darwinism may rule out some reductionist theories of the mind of the sort that are based on analogies with artificial intelligence, but it does not rule out the hope of other thoroughly reductionist views of mentality.

When Edelman says that a person cannot be reduced to molecular interactions, is he saying anything different (except in degree) than a botanist or a meteorologist who says that a rose or a thunderstorm cannot be reduced to molecular interactions? It may or may not be silly to pursue reductionist programs of research on complicated systems that are strongly conditioned by history, like brains or roses or thunderstorms. What is never silly is the perspective, provided by reductionism, apart from historical accidents these things ultimately are the way they are because of the fundamental principles of physics.

Roger Penrose strayed some time ago from his successful research in mathematical physics to think about the mind. As in his earlier books, he argued at the Jesus College symposium that " classical [that is, prequantum] physics seems incapable of explaining a phenomenon so deeply mysterious as consciousness". I gather that Edelman agrees with Penrose because he finds the determinism of classical physics uncongenial. Determinism is logically distinct from reductionism, but the two doctrines tend to go together because the reductionist goal of explanation is tied in with the determinist idea of prediction; we test our explanations by their power to make successful preductions. This must be what Edelman means when he speaks of modern physics (i.e., quantum mechanics) as refuting Enlightenment ideas of reductionism.

Of course, everything is ultimately quantum-mechanical; the question is whether quantum mechanics will appear directly in the theory of mind, and not just in the deeper-level theories like chemistry on which the theory of the mind will be based. Edelman and Penrose might be right about this, but I doubt it. It is precisely those systems that can be approximately described by pre-quantum classical mechanics that are so sensitive to initial conditions that, for practical purposes, they are unpredictable. In quantum mechanics isolated systems are governed by an equation (the Schroedinger equation) whose solutions are strictly speaking fully deterministic, never chaotic. The famous uncertainties in the positions and velocities of particles discovered by Heisenberg do not arise in isolation systems but only when we let such a system interact with a measuring apparatus.

There is another reason for some of the opposition to reductionism, and specifically to the perspective provided by grand reductionism. It is that this perspective removes much of the traditional motivation for belief in God. This is especially true, for example, of one of the great reductionist episodes in the history of science: first Darwin and Wallace explained the evolution of adaptation as a consequence of heredity and natural selection; then twentieth-century biologists explained heredity as a result of genes and mutations; and then Crick and Watson explained the genetic mechanism as a consequence of the structure of the DNA molecule, which with a large enough computer could be explained as a solution of the Schroedinger equation.

Vaclav Havel has described the corrosion of religious faith as a reason for his own reservations about much of science. In a 1987 article(4) he complained that "abolishes as mere fiction even the innermost foundation of our natural world; it kills God and takes his place on the vacant throne....' Then, last year, in a widely quoted speech he added that "we may know immeasurably more about the universe than our ancestors did, and yet it increasingly seems that they knew something more essential about it than we do, something that escapes us."(5)

On the other hand, some people are attracted to reductionist science for the same reason. This is an old story. Thales' ocean had no room for Poseidon. In Hellenistic times the cult leader Epicurus adopted the atomistic theory of Democritus as an antidote to belief in the Olympian gods. I think that Midgley is absolutely right in arguing that scientists are often driven in their work by motives of this sort. Of course, none of this bears on the question of whether the reductionist perspective is correct. And since in fact it is correct, we had all better learn to live with it.

There is one limitation of the scientific world view that I am glad to acknowledge. Science may be able to tell us how to explain or to get what we value, but it can never tell us what we ought to value. Moral or aesthetic statements are simply not of the sort which it is appropriate to call true or false. I think Midgley would agree, but I am not sure whether Atkins would, and certainly many others would not. According to the British press, the Bishop of Edinburgh recently argued that, since people are genetically preconditioned toward adultery, the Church should not condemn it. Whatever you think of adultery, it is simply a non sequitur to draw moral lessons from genetics. Ronald Reagan made the same silly mistake when he argued that abortion should be banned because science has not yet decided whether the fetus is alive. Whatever definition of life scientists may find convenient, and at whatever point in pregnancy a fetus may start to match that definition, the question of the value we should place on (say) a newly fertilized human egg is one that is entirely open to individual moral judgment. (Not that this is the only issue in the debate over abortion, or even the one that necessarily motivates opponents of abortion.) Science can't even justify science; the decision to explore the world as it is shown to us by reason and experiment is a moral one, not a scientific one.

None of the participants in the symposium at Jesus College seems to have addressed the really urgent problem confronting reductionism: Is it worth what it cost? After all, there are many competing reasons for doing science. Some research (e.g., medicine, much of chemistry) is done for practical purposes, or for use in other fields. Some of it (e.g., medicine again, especially psychiatry and psychology, human evolution) is done because we are naturally interested in ourselves. Some of it deals with things (e.g., the mind again, black holes, superconductivity) that are so weird and impressive that we can't help trying to understand them. Some research is done because we suspect the phenomena that we study (e.g., superconductivity again, turbulence, sex ratios in animal populations) will have explanations that are mathematically beautiful. All of these types of research compete for funds with research that is done because it moves us closer to the reductionist goal of finding the laws of nature that lie at the starting point of all chains of explanation.

The problem facing science is not (as most of the Jesus College symposiasts seem to think) that the reductionist imperative is putting the rest of science at risk. Few if any of us who are interested in the search for the laws of nature doubt the validity of the other motives of search. (I suspect that eventually I will come to feel that research on cancer or heart disease is more important than anything else.) The problem is that some people, including some scientists, deny that the search for the final laws of nature has its own special sort of value, a value that also should be taken into account in deciding how to fund research.

At present, the search for final explanations takes place chiefly in elementary particle physics. But research on elementary particles has become very expensive, because the laws of nature are revealed more clearly in the collisions of particles in high-energy accelerators than in what is going on around us in everyday life. Cosmology is also important here. As John Barrow reminded the symposium, in order to understand the world we need to know not only the laws of nature but also the initial conditions. Some theories hope that the initial conditions may ultimately be derived from the laws of nature, but we are a long way from that goal. Cosmological research too is very expensive, requiring observatories like Hubble and COBE and AXAF that are carried above the earth's atmosphere on artificial satellites.

For budgetary reason this sort of research is slowly coming to a halt in the US. The Supercollider project was canceled, partly because the arguments that such research is best done at existing laboratories or through international collaboration; but the same Congress that killed the Supercollider went on to cut research funding ot other national laboratories, and the present Congress has shown no eagerness to cooperate with Europe in building their next accelerator near Geneva, the Large Hadron Collider.

In the debates over these funding decisions, an important part was and is played by scientists, including some physicists, who oppose spending for elementary particle physics. In part, these scientists take this position because they hope to see this money spent on research in their own fields, a hope that was disappointed when the funds saved by canceling the Supercollider disappeared into the general budget. But also at work is a perfectly sincere lack of appreciation of the reductionist tradition in science, a tradition that in our time is embodied in the physics of elementary particles and fields. It is good that reductionism is discussed by talented people like those who met at Jesus College, but I wish that their discussion could have been more to the point.

(1) Freeman Dyson, "The Scientist as Rebel", The New York Review, May 25, 1995,pp. 31-33.

(2) This book contains interesting articles on the foundation of mathematics and on the other subjects, which I will not discuss here because I want to concentrate on reductionism in the natural sciences.

(3) Grand and petty reductionism correspond more or less to what the evolutionary biologist Ernst Mayr has called "theory reductionism" and "explanatory reductionism" in his article "The limits of Reductionism", Nature 331 (1987), p.475.

(4) "Politics and Conscience", in Vaclav Havel, or Living in Truth (Faber and Faber, 1987), p.138. I should add that Havel approves of some aspects of modern science: the anthropic principle and the Gaia hypothesis. This is cold comfort to the working scientist; Havel misunderstands the anthropic principle and overrates the Giai hypothesis.

(5) Speech at Independence Hall, Philadelphia, July 4 , 1994, excerpted in The New York Times, July 8, 1994, p.A.27.