"THE theory that a living organism meets the requirements of a specification is so extraordinary," the biologist-philosopher may say, "it flavours so much of mysticism that it should only be accepted after the most rigid proof."

No doubt. So should every theory. But as a biologist he believes this one already. So convinced is he that he does not even argue about it. The language he uses takes the reality of specifications for granted. The methods he adopts could not be justified if a living organism did not meet the requirements of a specification. And his success is sufficient proof that the biologist's tacit assumptions are sound. What is good enough for the biologist should, in this instance, be good enough for the philosopher.

So we need not weary the reader with recondite scientific facts and logic-chopping arguments. We will show him instead that, so long as we address ourselves to the biologist, we are preaching to the converted. Once again we will appeal from Philip drunk to Philip sober.

Let us discuss, first the language used by biologists, then the methods they follow and, lastly, how success proves their methods to be sound.

Whenever a biologist speaks of damage, or repair, or deformity, to mention three only of the many words which illustrate our point, he implies that there is a specification. For it is meaningless to apply these words to anything which does not have to meet specified requirements.

Whatever may be done to the end moraine of a glacier cannot constitute damage. But many things could conceivably be done to St. Paul's Cathedral which would constitute damage. The reason is obvious. Damage does not mean merely alteration. It means alteration of such a kind that the specified requirements are no longer met in their entirety. So, when there are no specified requirements there can be no damage. The end-moraine of a glacier may have any structure compatible with physical laws. Any change which is still compatible with these laws violates nothing. But the structure of St. Paul's Cathedral must also be compatible with Sir Christopher Wren's specification. A change, though it conforms to the laws of physics and chemistry, may still violate these requirements. We then say that the building has been damaged. Similarly a biologist who says of any living tissues that they have been damaged implies thereby that some requirements additional to those of physics and chemistry have been violated. If he did not mean this he would have no right to use the word "damaged". He would have to say "changed".

Similarly the word "repair" cannot be defined without reference to specified requirements. Let us attempt a definition. To repair a thing is to change it. But every change does not constitute repair. It must be a particular kind of change. It might be suggested that repair constitutes change back to some previous condition. But no, this would not be a true definition. A road was once a ploughed field. But one does not repair a road by ploughing it up. One repairs the road by remetalling to the Borough Engineer's specification. Repair always means change to a damaged thing so that it may conform to specified requirements. When a biologist uses the word he cannot mean anything else. If he did not believe that there were specified requirements he would have no right to use the word "repair". Again he would have to say "change". If there were no specifications damage and repair would amount to the same thing: mere alteration.

It is equally obvious that a biologist takes the reality of a specification for granted when he says that most living organisms are normal but that a few are deformed. It would be meaningless to say that the end moraines of most glaciers are normal but that a few are deformed, since for them any structure is permitted compatible with the laws of physics and chemistry. But a biologist does not think it meaningless to say that most men are normal but that a few have the deformity of a hunchback and a few the deformity of six fingers on a hand. He applies the word "deformity" to such features because he is convinced that there is a specification which requires a straight back and five fingers.

We need not go on elucidating the obvious. Everyone has known what we have said above all his life and we should have had no reason to insist on its significance were it not that the biologist often ignores it all when he turns philosopher.

Of course he may assert that someone will some day, somehow find means of eliminating the words damage, repair and deformity from biology. This is the old appeal to faith, hope and charity and we, personally, are not charitable enough to allow such vague speculations to pass either as science or philosophy. Though Philip drunk may clamour that biologists have no more right than geologists to speak of damage, repair and deformity without further rigid proof, we feel sure that Philip sober will continue to use these words and will not worry about proofs.

We come next to the methods used in biology. What is significant about them can best be illustrated by a little story.

Let us imagine two classrooms. In the one a professor of inorganic chemistry and in the other a professor of bio-chemistry are giving a demonstration. In the first room the professor takes the second bottle from the right off the top shelf. (The reason for mentioning these details will appear later.) It is a tall brown bottle and contains caustic soda solution. He pours some of the liquid from the bottle into a beaker filled with a clear fluid. This is a solution of ammonium carbonate. A striking change is observed. Everyone smells ammonia. This has been liberated by the chemical reaction.

In the other classroom a more elaborate and difficult experiment is in progress. It would take us too long to give a detailed description of it. The professor has secured some muscles taken from frogs' legs. One of these has been macerated, and shown to contain glucose. Another, with its nerve still attached, is suspended in a dilute salt solution in the presence of oxygen, and is repeatedly stimulated by a galvanic current applied to the nerve ending. At each stimulation the muscle contracts, and the professor proceeds to show the gradual appearance of lactic acid in the fluid perfusing the tissues. A chemical formula written on the blackboard shows how lactic acid and carbon dioxide are oxidation products of glucose.

After the demonstration in each class the professor asks one of the students what scientific law has been proved. The student in inorganic chemistry sets the class laughing. He says it was proved that the tall brown bottle, second from the right on the top shelf, contained caustic soda solution. He is reprimanded for his flippancy. But he might almost have been able to read thoughts, for that is exactly what the experiment did prove to the professor's relief. At the moment of pouring the professor remembered that a charwoman had recently disarranged some of the bottles. He was not quite sure that he had selected the right one until he smelt the ammonia. But he does not tell this to his students. It has nothing to do with the laws of chemistry, but is a matter of his laboratory organization. So he explains what he wants the class to infer from the experiment. This is that sodium being a strong base, displaces the weaker base ammonia from its salts.

The student in the bio-chemistry class is not particularly fortunate in his answer either. He says the demonstration with the muscles proved that glucose oxidizes to lactic acid. Were he in the other room he would probably be commended for an answer like this. But it is not the answer expected in the biology class. Consequently, the professor of bio-chemistry replies a little testily that he would not have taken the trouble to procure muscles from the legs of frogs to prove a simple law of chemical reaction. He could have done that more easily with glucose taken from a bottle. He reminds the class that he is there to teach them biology, not chemistry. For the purposes of a biological demonstration they must regard chemical reactions as accepted facts not requiring verification. They should remember, he tells them, that biological laws are not, like those of chemistry, generalizations about the substances concerned, but about the tissues in which these substances are to be found; not generalizations about the way chemical compounds react on each other, but about the circumstances in living bodies under which these reactions take place.

This anecdote shows that the things taught by biologists resemble the rules which govern the organization of a laboratory. These prescribe the specified place where each reagent shall be kept, the specified occasions when the stock is to be replenished, the specified sources from which new supplies are to be obtained, the specified ways in which waste and surplus materials are to be disposed of. Similarly, biology students are told of the specified requirements met in the organic world. They are told that there shall be glucose in muscles, phosphorus in the brain, calcium in bones; that the glucose shall be replenished from a stock of glycogen in the liver and that oxygen shall be obtained via the lungs; that waste products shall be eliminated through the appropriate excretory organs.

Biologists can tell us of specific requirements which govern the heating and ventilation of an organism, which control the timetable of its various functions, which ensure that its system shall be ready to receive new stocks of material at the proper moment. And they can tell us what will happen when there is a departure from the normal. They find, for instance, that it is fatal to prevent the skin from perspiring freely, that a goitre may form if iodine is not in its specified place, that absence of vitamins results in various deficiency diseases. They find, in fact, that interference with the specification laid down for the behaviour of living matter has consequences analogous to those which would result in a laboratory if the exhaust flues were not kept open when needed, if materials were not requisitioned in time, and if the bottles were allowed to become disarranged.

Hence much of the work of biologists is devoted to the discovery of the specified requirements for each organism and each type of tissue. Pioneers like Leonardo da Vinci have pointed the way to the proper method. It is to examine normal structure, normal processes, normal behaviour and to draw therefrom, conclusions as to the nature of the specification. As more and more detail is discovered, this can be transcribed more and more fully into words and drawings.

In the course of their work biologists have found some variation from individual to individual. They conclude that the specification for the species does not contain complete requirements for every detail but allows some latitude, just as the specification for a machine allows certain limits of tolerance. These limits vary both in engineering and in biology. The latitude allowed to the shape of a tree is, for instance, great while that allowed to the hydrogen-ion concentration of the blood is small.

It is often of practical importance to know what departures from the average may occur in normal individuals. So the biologist's task is not completed when he has studied one individual only. His method is to examine a large number and to note carefully all variations between them. Only then is he satisfied that he knows enough about the specification to make predictions with confidence.

The biologist-philosopher may argue that physicists sometimes follow a similar method and he may infer from this that physicists believe in the reality of specifications for the inorganic world just as much as biologists do for the organic world. We have met this suggestion and shall have to dispose of it later. But not in the present chapter. Here we are concerned with the methods and convictions of biologists only, not with those of physicists.

We will therefore be content to show, in conclusion, that the biologist's method leads to successful predictions which would be inconceivable if there were no specifications. To do this we will contrast the means available for predicting the future configuration of any system of moving particles when there is no specification with the means available when there is one.

Though the reader may possibly still believe that some inorganic systems (crystals, for instance) meet specified requirements, he is likely to agree that the stars forming our galaxy are allowed to have any arrangement compatible with physical laws. So the galaxy is a suitable example of an unspecified configuration.

The only means at the astronomer's disposal for predicting future positions of stars in our galaxy are Newton's laws of motion and such laws as are derivatives or modifications thereof. The astronomer applies his knowledge of these laws and of the present positions and motion of the bodies in our solar system to predict future positions. His task is difficult and laborious and requires much mathematics, but it is within his powers. His methods enable him to foretell when the sun, moon and earth will be in line and thus to prophesy eclipses. So long as he is dealing with comparatively few bodies, all chiefly acted on by one single one far more massive than the others, like the sun and its planets, the astronomer's method succeeds. When the system is more complicated it fails.

All future configurations of the whole galaxy are as rigidly determinate as those of the solar system, but no astronomer can say what they will be at any date in the remote future. The calculation is far too difficult. For with every change, the forces on each star change too. The task of computing the value and direction of each of the vast number of interacting forces from moment to moment and the effect they produce is beyond the powers of any human mathematician. It is not even possible to work out accurately how only three stars of approximately equal size would behave under the influence of their mutual gravitational attractions. All that can be said with certainty is that, as the conditions are constantly changing, the configuration too, must be constantly changing. The probabilities are overwhelmingly against a recurrence of the same picture during the whole of time. It is practically certain that any regularity of pattern which may exist at one moment will be lost the next.

Suppose now we take the astronomer to a spot where an acorn has been planted. We tell him that the place contains a collection of small particles which are free to move relatively to each other. We ask him to predict what their configuration will be in ten years' time. He will tell us that the task is beyond him. If we show him several such places he will say that only one thing can be prophesied with certainty. This is that after ten years there will be no trace of resemblance between the configurations at each of the places.

As we all know, the astronomer will probably be wrong. If the acorn planted in each spot lives and germinates an oak tree will stand there after ten years, and the trees will resemble each other most recognizably. We can, therefore, tell the astronomer that his deductive methods are quite inappropriate to our problem; we can tell him to put away his pencil and paper and substitute inductive reasoning based on experience with acorns. We can tell him that acorns and other living things are not like galaxies. They are determined more fully. We can tell him that biologists have means at their disposal which are not available to astronomers. We can tell him that a biologist predicts what will happen to the particles moving in living tissues without ever troubling about Newton's laws of motion. He bases his predictions on a knowledge of the specification.

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