Contents List:Analysing an AnalogyNo Evidence Regressive Philosophy Chance Fields of Force Shaking Down Superficiality |
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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 [John Desmond Bernal, 1901-71, Irish crystallographer. — Ed.], 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 do so, of course, only 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 We have only met the analogy among those writers who claim to have superseded mechanism and who are often referred to as "no crude materialists".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, and 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 application 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."
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 unco-ordinated 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.
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.
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. In a star which did not rotate, equilibrium would be reached when no part of the surface was further from the centre of gravity than any other, and 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 through which it falls 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, and neither 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 inter-molecular 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; neither 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 similar 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.
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 [1889-1976, British Unitarian minister and Marxist philosopher. — Ed.] 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 is meant by force in elementary physics. 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; that iron filings just fall on a magnet; that rubble just falls down the side of a ditch; that 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 belief in a law of complexity or an element of drill.
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, or 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.
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.
When we consider the process of assimilation of food, we can by no stretch of language describe this as shaking down. Things in biology 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 settle only 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. From no more than knowledge of the shape of amino-acid radicals, we could never predict how they were 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.