THE crystal analogy can be carried quite a long way. Both crystals and living organisms grow from small beginnings. A chip broken off a crystal will, if placed in a suitable medium, grow into a large new crystal just as a seed or a cutting from a shrub, if placed in the soil, may grow into a new plant. Two crystals placed side by side in a concentrated solution become welded into a single unit, while a branch cut from a garden rose can be grafted on to a wild rose root to form a single bush. When a crystal from which a piece has been broken off is placed in a concentrated solution, growth is most rapid at the "damaged" place. There is here, we are told, a process analogous to the healing of wounds.

From all this it has sometimes been inferred that living tissues do not only resemble crystals in a few superficial particulars, but that they are crystalline in their fundamental structure. Bernal, for instance, has proved by X-ray analysis that minute morsels of organic substance called viruses show a marked internal regularity. In a number of similar samples the same regularity is repeated, proving that there is a Problem of Repeated Form for viruses as well as for sparrows.

Bernal, however, does not draw this conclusion. The conclusion he does draw is that the viruses are, in effect, crystals. He must stretch a point to say so, for the regularity shown by viruses is not much like that found in inorganic crystals and is quite similar to that found in other organic substance. Nevertheless, from describing these bodies as crystals, Bernal has gone on to suggest that their crystalline structure may help to solve the mystery of Life. It could only do so, of course, if the process of virus production were the same as the process of crystal production. Bernal apparently thinks that it may be.

The crystal-analogy is not stressed by all materialists. Mechanists, in particular, who say that living organisms are mere machines deny that they are mere crystals. We have only met the analogy among those writers who claim to have superseded mechanism and who are often referred to as "no crude materialists". We must gather that it is more materialistic to say "mere machines" than to say "mere crystals".

The reason why these writers, who are by no means all biologists, appear less materialistic is that they take a mystical view of the nature of Matter. It seems to them that the beautiful regularity observable in crystals and elsewhere can never be the work of the monkey of chance. They deny by implication, if not explicitly that, in the inorganic world, things fly about indiscriminately. They believe that the laws of physics and chemistry embody a principle of guidance, selection, control which results in occasional defiance of the laws of probability in favour of certain preferred formations.

Thus Broad in The Mind and its Place in Nature speaks on page 93 of "a general tendency for complexes of one order under suitable conditions to form complexes of the next order". Similarly J. S. Haldane has said somewhere: "The tendency to take specific forms or arrangements is always present in molecules and, therefore, in matter." In The Origin and Nature of Life Benjamin Moore said on page 188: "It may be summed up as a general law universal in its apphcation to all matter, although varying in intensity in different types of matter, and holding throughout all space as generally as the law of gravitation - a law which might be called the 'Law of Complexity' that matter so far as its energy environment will permit tends to assume more and more complex forms in labile equilibrium. Atoms, molecules, colloids, and living organisms arise as the result of the operations of this law, and in the higher regions of complexity it induces organic evolution and all the many thousands of living forms. At still higher levels, it forms the basis of social evolution and leads to that intellectual development which surmounts the whole and is ever building upwards."

Fine words these, but without one shred of evidence to support them. Non-living collections of particles do not become more complex as time goes on, if, indeed, the words "simple" and "complex" can be applied to them at all. There is nothing to show that even the whole Material Universe was simpler in bygone days than it is now. In the absence of Life, material particles tend as much to fly apart as to come together. The only general way in which we can describe their behaviour is to say that they fly about. Living substance may become more complex as time goes on, of course. Moore generalized unjustifiably. He drew conclusions from observations made in the organic world only and formulated these into a law which he tried, with no facts to support him, to apply to all Matter.

The assertion which we have quoted already from Broad that Matter has a natural tendency to fall into the form of organisms has no evidence to support it either. The opposite is true. Matter left to itself and moved only by the uncoordinated pushes and pulls applied to it by other Matter has a natural tendency to fall out of the form of organisms, as is shown when a creature dies and its substance becomes less and less organized. There is a natural tendency for Matter to fall into the form of organisms in the presence of Life. But there is the opposite tendency whenever Life is absent.

However, the classification of assemblies of particles into different orders, often distinguished as "higher" and "lower," is an integral part of a philosophical outlook which is becoming more and more fashionable among those whose knowledge of physics is limited. It is a return to the outlook of the Middle Ages and is responsible for most of the muddled thinking which, nowadays, passes as philosophy. It has come to permeate contemporary thought and must, therefore, occupy a great deal of our attention in these pages. At the moment we are only concerned with the way in which these strange theories about the laws and principles of physics have been applied to crystal formation, and in this connection we cannot do better than to quote Dr. Joseph Needham. On page 111 of his book The Great Amphibian he says: "In crystal formation on this view, we have one form of organization higher than that which exists in the homogeneous gas or liquid, where molecules are aimlessly rushing hither and thither. An element of drill has entered into the system when it crystallizes into a lattice structure." The inference to be drawn is that in living substance we have a still higher form of organization, that molecules behave even less aimlessly, that a more fully disciplined element of drill enters into the system and that, therefore, the production of living substance conforms to a principle of physics already manifest to a less marked degree in the production of crystals. The aim of all philosophers belonging to this school is to prove that the distinction between living and hfeless bodies is of degree only and not fundamental.

Our own view is that in the organic world it is quite legitimate to speak of higher and lower forms of organization, that in this world molecules do not behave aimlessly, and that "an element of drill" is not such a bad way of describing how they do behave. What we quarrel with is the suggestion that this way of talking can also be applied to the inorganic world. We assert that when, in the absence of Life, molecules rush hither and thither they always do so "aimlessly". We deny that they ever pursue an aim or conform to an element of drill in any sense of the word.

We wonder whether Needham would attribute an element of drill to other regular structures which can be found here and there in the inorganic world. Stars have, for instance, the shape which would result from rotating an ellipse about its shorter axis. They are flattened spheres, orange-shaped. Raindrops are pear-shaped. Would it be considered plausible to argue that one need only discover why a number of stars are all similar or why a number of raindrops are all similar in order to know why a number of sparrows are all similar? Anyone who knew no physics at all might think so. If he knew just a little physics he would realize that the processes which lead to the formation of stars and raindrops can be wholly attributed to the monkey of chance.

The shape of a star is due to the combined action of gravitation and centrifugal force. The former pulls each particle towards the common centre of gravity. As the substance forming the star can flow, each portion gets as near to this centre as neighbouring substance will permit. Equilibrium would be reached in a star which did not rotate, when no part of the surface was further from the centre of gravity than any other. The result would be a perfect sphere. As every star rotates about its axis, centrifugal force opposes gravity in the plane of rotation, but not in the direction of the axis. This causes the sphere to be slightly flattened. A star represents a stable configuration in which there is equilibrium between the various forces acting on each particle. If it were distorted the star would return to its original shape after the disturbing force had been removed.

A raindrop is similarly stable. It acquires that shape in which the forces due to gravity, surface tension and friction with the air it falls through are in equilibrium.

Particles "rushing hither and thither aimlessly" are bound to reach an orange or pear shape under the respective conditions pertaining when stars or raindrops form. The behaviour of such particles does not in any way fail to conform to the laws of probability. There is no need to invoke an element of drill in order to explain what happens. Nor is this necessary for an explanation of crystal structure.

Solid crystals form either when a substance solidifies from its liquid or gaseous state or when it precipitates out of a concentrated solution. While the substance is gaseous, or liquid, or in solution the molecules tumble and dart about erratically. Occasionally one of them comes near enough to the growing crystal to be attracted to it by an intermolecular force. The molecule is then held firmly in position and becomes a part of the solid structure.

Molecules do not usually have a very symmetrical shape, and the intermolecular forces are not equally strong between all sides; nor do molecules pack equally well together in all positions. It is, therefore, natural that, when falling into the growing crystal structure, the molecules jostle and tilt until they mostly come to be held in position by those sides which attach most firmly. Then we get a pattern of considerable regularity in which all like molecules are held the same side up. The resultant structure, consisting of closely packed similar molecules, is the most stable which the conditions of its formation permit. Molecules of sodium chloride rushing aimlessly hither and thither are bound to tumble into the well- known configuration of a rock salt crystal. The structure of this is no more determined by an element of drill than is the structure of a star or a raindrop.

It is true, of course, that crystal formation illustrates a tendency which is followed by all Matter throughout the inorganic world. But this tendency is very different from the "tendency for complexes of one order to form complexes of the next order" of which Broad speaks. We must seek to discover what this principle is. For only a proper understanding of the nature of Matter can lead us to appreciate the full and true meaning of the Problem of Repeated Form.

A molecule of sodium chloride is precipitated on to the growing rock salt crystal because it is attracted thereby, just as iron filings are attracted by a magnet and falling stones are attracted by the earth. The attraction can be measured in terms of the force between the two objects and can be expressed in terms of the condition in the space between them. A serviceable mode of expression is to say that there is a field of force between the rock salt crystal and an approaching sodium chloride molecule, between a magnet and the iron filings, between the earth and a falling stone. The intensity and direction of such a field can be detected by suitable measuring instruments. The moving object follows the direction of the field and its acceleration is proportional to the intensity of the field.

In a field of force there is an equal pull on each object in the direction of the other. Thus each sodium chloride molecule pulls on the rock salt crystal as strongly as the crystal pulls on the molecule; an iron filing pulls on the magnet as strongly as the magnet pulls on the iron fihng; stones rolling down the side of a ditch pull as strongly on the earth as the earth pulls on the stones. In each instance the only reason why the one object moves and not the other is that the one is more easily dislodged than the other.

In elementary text-books this is expressed in the phrase "action and reaction are equal and opposite". Were we writing for physicists only we should have no need to mention it. But among non-physicists the nature of a physical force is rarely understood. Thus John Lewis says in his Introduction to Philosophy on page 9, that in the physical world "the greater force always overcomes the lesser". The context makes it still clearer that he does not know what in elementary physics is meant by force. Yet this same philosopher declares a few pages later that Eddington's view of the nature of the Material Universe is all wrong!

When the movement of a thing is entirely determined by the intensity and direction of a field of force we can legitimately say that it just falls. To say that sodium chloride molecules are precipitated on to a growing rock salt crystal is the same as to say that they just fall there; iron filings just fall on a magnet; rubble just falls down the side of a ditch; the nebulous substance forming a new star just falls towards the common centre of gravity until it can fall no further. In falling, things in the inorganic world invariably shake down into a more and more stable configuration.

This is the principle followed in the formation of stars, raindrops, crystals and all other lifeless systems in nature. Invariably their component parts just shake down. These words express the true law apphcable to all Matter. Only in those biologist-philosophers whose imagination outstrips their knowledge can we find behef in a law of complexity or an element of drill.

"Shaking down" does not sound like a scientific term and we could, if we wished to be impressive, replace it by more orthodox physical language. We could explain that falling means a reduction in potential energy; we could show how a process of shaking down illustrates the second law of thermodynamics, and how in the formation of stars, raindrops and crystals the entropy of a system increases. We could even go on to explain that for quantum physics such terms as "particle", "force", "falling" must be translated into other language. But in doing so we should not come one step nearer to a justification of the theories of Moore, Needham and other philosophers of the same school. All we could do would be to repeat the arguments we have given above in a more obscure form. Neither the laws of thermo-dynamics, nor the quantum theory nor other even more difficult aspects of modern physics contain anything to justify the behef that inorganic Matter ever conforms to an element of drill, or that it tends to form complexes of higher and higher order, or that it tends to fall into the form of organisms.

Nothing which physicists have discovered justifies such mystical theories about the nature of Matter. We should have been spared them altogether were it not that scientific principles which are imperfectly understood have served so many writers on philosophy as a means of confusing and misrepresenting simple facts to themselves and their followers. We prefer, therefore, to retain the expression "shaking down". It is comprehensible to physicists and non-physicists alike and we should still mean the same thing if we were to translate this term into the language of thermo-dynamics or the quantum theory, if we were to use the longest and most incomprehensible words we could think of.

The mystical view of the nature of Matter has become very deeply ingrained in our modern philosophers, be they of the biologist or any other variety. This, we suspect, and not his lapses in logic, is the true reason why Eddington's explanation of the meaning of physics is so often disparaged; this is why men who have no conception of what a force is in physical language do not hesitate to set their fancies up against Eddington's facts. The one fact against which the modern mystic will fight to the last ditch is that, in the inorganic world, things which move merely fly about and things as they cease to move merely shake down.

To return now to the analogy between crystals and living organisms. Everyone knows that this analogy is quite superficial. Everyone knows that the process of crystal formation just described is not in the least like the process by which sparrows are formed. The biologist-philosopher knows it and ignores it when he ceases to be a biologist and turns philosopher. As a biologist he does not think that sparrows are precipitated out of a concentrated solution of sparrow essence. And, though he may not have studied crystallography, he does at least know that crystals do not sally forth in search of food. So we need only appeal from Philip drunk, the philosopher, to Philip sober, the scientist, in order to learn in full detail how much the two processes differ.

The molecules of sodium chloride which form a rock salt crystal must be available in the immediate vicinity of the growing crystal. Consequently this forms in a concentrated solution of its substance. But the things which form a sparrow's body do not have to be available in its immediate vicinity. These things come from here, there and everywhere; from the food eaten, the water drunk, the air breathed. What will be sparrow to-morrow may to-day be a grain of corn in the gutter, a drop of water in the village pond, some oxygen in the air above the telegraph wires.

Moreover sparrows do not attract grains of corn as a rock salt crystal attracts molecules of sodium chloride. It would be truer to say that grains of corn attract sparrows. However, this is a different kind of attraction of which physicists know nothing. There is no field of force detectable by suitable measuring instruments between a sparrow perched on the telegraph wires and a grain of corn lying in the gutter. No one believes that there is a pull on the grain of corn towards the sparrow and an exactly equal pull on the sparrow towards the grain of corn. Food certainly does not just fall into a living organism.

And when we consider the process of assimilation of food we can by no stretch of language describe this as shaking down. Things do not fall until they can fall no further. There is no inevitable tendency towards greater stability. Living tissues are often less stable than the substances from which they have been formed.

Then again, the shape of the constituent particles has not the same effect on the structure of living substance as it would if the process were merely one of shaking down. Molecules of sodium chloride can only settle into one particular crystalline structure, for their shape allows them to pack in one way only. From a knowledge of this shape it would be quite safe to predict the structure of the resultant crystal. But any of the twenty known amino-acids may form part of a great variety of protein structures. We could never predict from knowledge of the shape of the amino-acid radical only how it was going to pack. We should also have to know what animal and what tissues they packed into. In the organic world structure is clearly not determined only by the shape of the constituent particles.

Lastly, the shape and size of a crystal as of any lifeless body are completely dependent on the circumstances at its formation. Consequently two rock salt crystals can only resemble each other closely if formed from solutions of identical purity, of identical concentration and at identical temperatures. Otherwise they will be of different shapes and sizes. But any two living organisms may be practically identical even if their past history has differed considerably. No two sparrows have had identical experiences. They may have been hatched in different places, exposed to different weather, chased by different cats, found different food in different gutters. Yet they are as similar as two adjoining villas in a suburban street. We must conclude that the influence which prevents shaking down has some mastery over circumstances.

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