THE GENERAL CHARACTER AND THE PURPOSE OF THE INVESTIGATION

This little book arose from a course of public lectures, delivered by a theoretical physicist to an audience of about four hundred which did not substantially dwindle, though warned at the outset that the subject-matter was a difficult one and that the lectures could not be termed popular, even though the physicist's most dreaded weapon, mathematical deduction, would hardly be utilized. The reason for this was not that the subject was simple enough to be explained without mathematics, but rather that it was much too involved to be fully accessible to mathematics. Another feature which at least induced a semblance of popularity was the lecturer's intention to make clear the fundamental idea, which hovers between biology and physics, to both the physicist and the biologist.

For actually, in spite of the variety of topics involved, the whole enterprise is intended to convey one idea only — one small comment on a large and important question. In order not to lose our way, it may be useful to outline the plan very briefly in advance.

The large and important and very much discussed question is: How can the events in space and time which take place within the spatial boundary of a living organism be accounted for by physics and chemistry?

As a reward for the serious trouble I have taken to expound the purely scientific aspects of our problem sine ira et studio, I beg leave to add my own, necessarily subjective, view of the philosophical implications.

According to the evidence put forward in the preceding pages the space-time events in the body of a living being which correspond to the activity of its mind, to its self-conscious or any other actions, are (considering also their complex structure and the accepted statistical explanation of physico-chemistry) if not strictly deterministic at any rate statistico-deterministic. To the physicist I wish to emphasize that in my opinion, and contrary to the opinion upheld in some quarters, quantum indeterminacy plays no biologically relevant role in them, except perhaps by enhancing their purely accidental character in such events as meiosis, natural and X-ray-induced mutation and so on - and this is in any case obvious and well recognized.

For the sake of argument, let me regard this as a fact, as I believe every unbiased biologist would, if there were not the well-known, unpleasant feeling about ‘declaring oneself to be a pure mechanism’. For it is deemed to contradict Free Will as warranted by direct introspection.

James Clerk Maxwell made momentous contributions to the development of electromagnetic theory: In formulating the set of equations that bear his name, he established a systematic and enduring foundation for modern electromagnetic theory; in developing the formalism to embrace optics, he demonstrated the range and power of his mathematized field theory, adumbrating its profound implications for subsequent developments ranging from relativity theory to communications technology. Maxwell's activity in this area spanned a period of twenty-five years – from the mid-1850s until his death in 1879 – and his thinking on the subject was developing and changing throughout that period. It is possible, nevertheless, to identify one crucial period of innovation: a period of about one year, centering on the summer of 1861, during which Maxwell was working on, and publishing in successive installments, a paper entitled “On Physical Lines of Force.” It was during that period that Maxwell modified one of the fundamental electromagnetic equations through the introduction of a new term called the displacement current, thereby rendering the set of foundational equations complete and consistent; and it was also during that period, in conjunction with the introduction of the displacement current, that Maxwell took the crucial first steps toward the unification of electromagnetism and optics.

PERMANENCE UNEXPLAINABLE BY CLASSICAL PHYSICS

Thus, aided by the marvellously subtle instrument of X-rays (which, as the physicist remembers, revealed thirty years ago the detailed atomic lattice structures of crystals), the united efforts of biologists and physicists have of late succeeded in reducing the upper limit for the size of the microscopic structure, being responsible for a definite large-scale feature of the individual - the ‘size of a gene’ - and reducing it far below the estimates obtained on pp. 29-30. We are now seriously faced with the question: How can we, from the point of view of statistical physics, reconcile the facts that the gene structure seems to involve only a comparatively small number of atoms (of the order of 1,000 and possibly much less), and that nevertheless it displays a most regular and lawful activity — with a durability or permanence that borders upon the miraculous?

Let me throw the truly amazing situation into relief once again. Several members of the Habsburg dynasty have a peculiar disfigurement of the lower lip (‘Habsburger Lippe’). Its inheritance has been studied carefully and published, complete with historical portraits, by the Imperial Academy of Vienna, under the auspices of the family. The feature proves to be a genuinely MendeIian ‘allele’ to the normal form of the lip.

THE PROBLEM

The world is a construct of our sensations, perceptions, memories. It is convenient to regard it as existing objectively on its own. But it certainly does not become manifest by its mere existence. Its becoming manifest is conditional on very special goings-on in very special parts of this very world, namely on certain events that happen in a brain. That is an inordinately peculiar kind of implication, which prompts the question: What particular properties distinguish these brain processes and enable them to produce the manifestation? Can we guess which material processes have this power, which not? Or simpler: What kind of material process is directly associated with consciousness?

A rationalist may be inclined to deal curtly with this question, roughly as follows. From our own experience, and as regards the higher animals from analogy, consciousness is linked up with certain kinds of events in organized, living matter, namely, with certain nervous functions. How far back or ‘down’ in the animal kingdom there is still some sort of consciousness, and what it may be like in its early stages, are gratuitous speculations, questions that cannot be answered and which ought to be left to idle dreamers. It is still more gratuitous to indulge in thoughts about whether perhaps other events as well, events in inorganic matter, let alone all material events, are in some way or other associated with consciousness. All this is pure fantasy, as irrefutable as it is unprovable, and thus of no value for knowledge.

The reason why our sentient, percipient and thinking ego is met nowhere within our scientific world picture can easily be indicated in seven words: because it is itself that world picture. It is identical with the whole and therefore cannot be contained in it as a part of it. But, of course, here we knock against the arithmetical paradox; there appears to be a great multitude of these conscious egos, the world however is only one. This comes from the fashion in which the world-concept produces itself. The several domains of ‘private’ consciousnesses partly overlap. The region common to all where they all overlap is the construct of the ‘real world around us’. With all that an uncomfortable feeling remains, prompting such questions as: Is my world really the same as yours? Is there one real world to be distinguished from its pictures introjected by way of perception into every one of us? And if so, are these pictures like unto the real world or is the latter, the world ‘in itself’, perhaps very different from the one we perceive?

Such questions are ingenious, but in my opinion very apt to confuse the issue. They have no adequate answers. They all are, or lead to, antinomies springing from the one source, which I called the arithmetical paradox; the many conscious egos from whose mental experiences the one world is concocted. The solution of this paradox of numbers would do away with all the questions of the aforesaid kind and reveal them, I dare say, as sham questions.

The molecular-vortex model provided the context for the first appearance of both the displacement current and the electromagnetic theory of light. The first form of the electromagnetic theory of light – which differs from the modern form no less than the first form of the displacement current differs from its modern counterpart – appeared in Part III of “Physical Lines,” published in January 1862. In brief, the newly introduced elastic property of the magnetoelectric medium allowed for the propagation of transverse shear waves in that medium; calculating, from the parameters of the model, the velocity of such waves – and finding close agreement with the measured velocity of light – Maxwell identified these waves in the magnetoelectric medium as light waves, and he concluded that the magnetoelectric and luminiferous media were one and the same. The broad nineteenth-century background bearing on such a connection between electromagnetism and light is taken up in Section 1 of this chapter. Section 2 then broaches the question of the precise role of the molecular-vortex model in the origin of the electromagnetic theory of light: Was the electromagnetic theory of light, as textbook accounts might suggest, from the outset basically a matter of deriving wavelike solutions from the equations of electricity and magnetism – in which case the mechanical model could have played at most an ancillary role in the genesis of the theory – or did the molecular-vortex model in fact play a more essential role in the initial formulation of the electromagnetic theory of light, as suggested by the fact that the theory made its first appearance in Part III of “Physical Lines”?

The immediate context for Maxwell's initial modification of Ampère's law (Ampère's circuital law in differential form), through the introduction of a new term to be known as the “displacement current,” was, as we have seen, his work on the theory of molecular vortices: His proximate aim in modifying Ampère's law was to extend the theory of molecular vortices to electrostatics, and his explicit interpretation at that point of the modified equation was as a mechanical calculation in the theory of molecular vortices, with the new term expressing the flux of the small idle-wheel particles owing to progressive elastic deformation of the vortices. All of the principal symbols and equations in “Physical Lines,” however, had dual significance – mechanical and electromagnetic – and the modified Ampère's law, in its electromagnetic character, had broader connections and significance, transcending its proximate matrix in the theory of molecular vortices. That broader context must be taken into account if we are to achieve a full understanding of the origin of the displacement current and its significance in the history of electromagnetic theory.

The question of the origin of the displacement current has been, and continues to be, the object of much interest and concern: Each year many thousands of students in physics courses throughout the world learn that Maxwell, on the basis of theoretical considerations, modified Ampère's law, through the introduction of a new term called the displacement current, and thereby perfected the enduring foundation for modern electromagnetic theory.

THE GENERAL PICTURE OF THE HEREDITARY SUBSTANCE

From these facts emerges a very simple answer to our question, namely: Are these structures, composed of comparatively few atoms, capable of withstanding for long periods the disturbing influence of heat motion to which the hereditary substance is continually exposed? We shall assume the structure of a gene to be that of a huge molecule, capable only of discontinuous change, which consists in a rearrangement of the atoms and leads to an isomeric molecule. The rearrangement may affect only a small region of the gene, and a vast number of different rearrangements may be possible. The energy thresholds, separating the actual configuration from any possible isomeric ones, have to be high enough (compared with the average heat energy of an atom) to make the change-over a rare event. These rare events we shall identify with spontaneous mutations.

The later parts of this chapter will be devoted to putting this general picture of a gene and of mutation (due mainly to the German physicist M. Delbrück) to the test, by comparing it in detail with genetical facts. Before doing so, we may fittingly make some comment on the foundation and general nature of the theory.

A REMARKABLE GENERAL CONCLUSION FROM THE MODEL

Let me refer to the phrase on p. 62, in which I tried to explain that the molecular picture of the gene made it at least conceivable that the miniature code should be in one-to-one correspondence with a highly complicated and specified plan of development and should somehow contain the means of putting it into operation. Very well then, but how does it do this? How are we going to turn ‘conceivability’ into true understanding?

Delbrück's molecular model, in its complete generality, seems to contain no hint as to how the hereditary substance works. Indeed, I do not expect that any detailed information on this question is likely to come from physics in the near future. The advance is proceeding and will, I am sure, continue to do so, from biochemistry under the guidance of physiology and genetics.

No detailed information about the functioning of the genetical mechanism can emerge from a description of its structure so general as has been given above. That is obvious. But, strangely enough, there is just one general conclusion to be obtained from it, and that, I confess, was my only motive for writing this book.

Few working papers survive from the period when Maxwell was working on “Physical Lines.” My own search of relevant archives, as well as the more exhaustive search conducted by Peter Harman in connection with his edition in progress of The Scientific Letters and Papers of James Clerk Maxwell, 3 vols. (Cambridge University Press, 1990–), turned up nothing beyond the material to which attention is directed by A. E. B. Owens's handlist to Add. MSS 7655 at the University Library, Cambridge. Of a set of five folios constituting Add. MSS 7655, V, c/8, two folios clearly correspond to the period when Maxwell was working on “Dynamical Theory” (see Appendix 2), and a third, dealing with “Helmholtz's Wirbelfäden [Vortex Filaments],” appears to date from a later period as well (1864–70 – Peter Harman, private communication; see also Letters and Papers of Maxwell, 2). The two remaining folios (both blank verso) evidently are associated with “Physical Lines.” One of these clearly relates to the treatment of motional electromotive forces that appears in “Physical Lines,” Part II, 476–85; this draft fragment refers explicitly to “equations (55),” which appear on p. 476 of the published version, and arrives at a form of the published equations (77), on p. 482.

The remaining folio is quite informative concerning various aspects of Maxwell's work on the molecular-vortex model; a photograph of it is presented in Fig. A 1.1, and I here transcribe it in full (cf. also the transcription in Harman, ed., Letters and Papers of Maxwell, 1 693).

NEW LAWS TO BE EXPECTED IN THE ORGANISM

What I wish to make clear in this last chapter is, in short, that from all we have learnt about the structure of living matter, we must be prepared to find it working in a manner that cannot be reduced to the ordinary laws of physics. And that not on the ground that there is any ‘new force’ or what not, directing the behaviour of the single atoms within a living organism, but because the construction is different from anything we have yet tested in the physical laboratory. To put it crudely, an engineer, familiar with heat engines only, will, after inspecting the construction of an electric motor, be prepared to find it working along principles which he does not yet understand. He finds the copper familiar to him in kettles used here in the form of long, long wires wound in coils; the iron familiar to him in levers and bars and steam cylinders is here filling the interior of those coils of copper wire. He will be convinced that it is the same copper and the same iron, subject to the same laws of Nature, and he is right in that. The difference in construction is enough to prepare him for an entirely different way of functioning.

THE CLASSICAL PHYSICIST'S EXPECTATION, FAR FROM BEING TRIVIAL, IS WRONG

Thus we have come to the conclusion that an organism and all the biologically relevant processes that it experiences must have an extremely ‘many-atomic’ structure and must be safeguarded against haphazard, ‘single-atomic’ events attaining too great importance. That, the ‘naïve physicist’ tells us, is essential, so that the organism may, so to speak, have sufficiently accurate physical laws on which to draw for setting up its marvellously regular and well-ordered working. How do these conclusions, reached, biologically speaking, a priori (that is, from the purely physical point of view), fit in with actual biological facts?

At first sight one is inclined to think that the conclusions are little more than trivial. A biologist of, say, thirty years ago might have said that, although it was quite suitable for a popular lecturer to emphasize the importance, in the organism as elsewhere, of statistical physics, the point was, in fact, rather a familiar truism. For, naturally, not only the body of an adult individual of any higher species, but every single cell composing it contains a ‘cosmical’ number of single atoms of every kind.

Nine years ago I put forward two general principles that form the basis of the scientific method, the principle of the under-standability of nature, and the principle of objectivation. Since then I have touched on this matter now and again, last time in my little book Nature and the Greeks. I wish to deal here in detail with the second one, the objectivation. Before I say what I mean by that, let me remove a possible misunderstanding which might arise, as I came to realize from several reviews of that book, though I thought I had prevented it from the outset. It is simply this: some people seemed to think that my intention was to lay down the fundamental principles which ought to be at the basis of scientific method or at least which justly and rightly are at the basis of science and ought to be kept at all cost. Far from this, I only maintained and maintain that they are — and, by the way, as an inheritance from the ancient Greeks, from whom all our Western science and scientific thought has originated.

The misunderstanding is not very astonishing. If you hear a scientist pronounce basic principles of science, stressing two of them as particularly fundamental and of old standing, it is natural to think that he is at least strongly in favour of them and wishes to impose them. But on the other hand, you see, science never imposes anything, science states.

Can science vouchsafe information on matters of religion? Can the results of scientific research be of any help in gaining a reasonable and satisfactory attitude towards those burning questions which assail everyone at times? Some of us, in particular healthy and happy youth, succeed in shoving them aside for long periods; others, in advanced age, have satisfied themselves that there is no answer and have resigned themselves to giving up looking for one, while others again are haunted throughout their lives by this incongruity of our intellect, haunted also by serious fears raised by time-honoured popular superstition. I mean mainly the questions concerned with the ‘other world’, with ‘life after death’, and all that is connected with them. Notice please that I shall not, of course, attempt to answer these questions, but only the much more modest one, whether science can give any information about them or aid our — to many of us unavoidable — thinking about them.

To begin with, in a very primitive way it certainly can, and has done so without much ado. I remember seeing old prints, geographical maps of the world, so I believe, including hell, purgatory and heaven, the former being placed deep underground, the latter high above in the skies. Such representations were not meant purely allegorically (as they might be in later periods, for example, in Dürer's famous All-Saints picture); they testify to a crude belief quite popular at the time.

I lived far apart from my best friend, actually the only close friend I ever had, for the greater part of my life. (Maybe that is why I have often been accused of flirtatiousness instead of true friendship.) He studied biology (botany to be exact); I physics. And many a night we would stroll back and forth between Gluckgasse and Schlüsselgasse engrossed in philosophical conversation. Little did we know then that what seemed original to us had occupied great minds for centuries already. Don't teachers always do their best to avoid these topics for fear that they might conflict with religious doctrines and cause uncomfortable questions? This is the main reason for my turning against religion, which has never done me any harm.

I am not sure whether it was right after the First World War or during the time I spent in Zurich (1921—7) or even later in Berlin (1927-33) that Fränzel and I spent a long evening together again. The small hours of the morning found us still talking in a café on the outskirts of Vienna. He seemed to have changed a lot with the years. After all, our letters had been few and far between and of very little substance.

I might have added earlier that we also spent our time together reading Richard Semon. Never before or after did I read a serious book with anyone else. Richard Semon was soon banned by the biologists, since his views, as they saw them, were based on the inheritance of acquired characteristics.

Manuscript material relating to “Dynamical Theory” and of interest in connection with Chapter 6, Section 1, includes four pages in the Maxwell manuscript materials at the University Library, Cambridge (in Add. MSS 7655, V, c/8; c/11; and V, f/4), to which I shall make reference as follows: Three pages, apparently representing parts of an early draft of “Dynamical Theory,” and corresponding to pp. 559–61, 568, and 569, I shall denote “[DT, A],” “[DT, B],” and “[DT, C]”; a fourth, apparently representing part of a later draft of “Dynamical Theory,” and corresponding to p. 578, I shall denote “[DT, D].” The correspondences to the cited parts of “Dymanical Theory” are not in doubt; that A, B, and C are earlier is suggested by the numbering of the equations, which differs from the published version, whereas D agrees with the published version in numbering of equations. A and B are pages numbered 22 and 23 (evidently in Maxwell's hand), in V, c/8; C is a page numbered 24, in V, f/4, but helpfully identified in the handlist to Add. MSS 7655 as belonging with A and B. D is in V, c/11. Also of interest is the manuscript of “Dynamical Theory” that was submitted to the Royal Society and is preserved there – PT. 72.7 – to which I shall refer as “Dynamical Theory [MS].” (I am informed that much of this material will be published in Harman, ed., Letters and Papers of Maxwell, 2.)

When I was a young mathematics student in the early 1950s I did not read a great deal, but what I did read - at least if I completed the book — was usually by Erwin Schrödinger. I always found his writing to be compelling, and there was an excitement of discovery, with the prospect of gaining some genuinely new understanding about this mysterious world in which we live. None of his writings possesses more of this quality than his short classic What is Life? — which, as I now realize, must surely rank among the most influential of scientific writings in this century. It represents a powerful attempt to comprehend some of the genuine mysteries of life, made by a physicist whose own deep insights had done so much to change the way in which we understand what the world is made of. The book's cross-disciplinary sweep was unusual for its time — yet it is written with an endearing, if perhaps disarming, modesty, at a level that makes it accessible to non-specialists and to the young who might aspire to be scientists. Indeed, many scientists who have made fundamental contributions in biology, such as J. B. S. Haldane and Francis Crick, have admitted to being strongly influenced by (although not always in complete agreement with) the broad-ranging ideas put forward here by this highly original and profoundly thoughtful physicist.