The present discussion may be started with one of those trivial questions which are often only too difficult to answer scientifically. What is the difference between a normal, a sick and a dead organism? From the standpoint of physics and chemistry the answer is bound to be that the difference is not definable on the basis of so-called mechanistic theory. Speaking in terms of physics and chemistry, a living organism is an aggregate of a great number of processes which, sufficient work and knowledge presupposed, can be defined by means of chemical formulas, mathematical equations, and laws of nature. These processes, it is true, are different in a living, sick or dead dog; but the laws of physics do not tell a difference, they are not interested in whether dogs are alive or dead. This remains the same even if we take into consideration the latest results of molecular biology. One DNA molecule, protein, enzyme or hormonal process is as good as another; each is determined by physical and chemical laws, none is better, healthier or more normal than the other.
Nevertheless, there is a fundamental difference between a live and a dead organism; usually, we do not have any difficulty in distinguishing between a living organism and a dead object. In a living being innumerable chemical and physical processes are so “ordered” as to allow the living system to persist, to grow, to develop, to reproduce, etc. What, however, does this notion of “order” mean, for which we would look in vain in a textbook of physics? In order to define and explain it we need a model, a conceptual construct. One such model was used since the beginnings of modern science. This was the model of the living machine. Depending on the state of the art, the model found different interpretations. When, in the seventeenth century, Descartes introduced the concept of the animal as a machine, only mechanical machines existed. Hence the animal was a complicated clockwork. Borelli, Harvey and other so-called iatro- physicists explained the functions of muscles, of the heart, etc., by mechanical principles of levers, pumps and the like. One can still see this in the opera, when in the Tales of Hoffmann the beautiful Olympia turns out to be an artfully constructed doll, an automaton as it was called at the time. Later, the steam engine and thermodynamics were introduced, which led to the organism being conceived as a heat engine, a notion which lead to caloric calculations and other things. However, the organism is not a heat engine, transforming the energy of fuel into heat and then into mechanical energy. Rather it is a chemodynamic machine, directly transforming the energy of fuel into effective work, a fact on which, for example, the theory of muscle action is based. Lately, self-regulating machines came to the fore, such as thermostats, missiles aiming at a target and the servomechanisms of modern technology. So the organism became a cybernetic machine, explanatory of many homeostatic and related phenomena. The most recent development is in terms of molecular machines. When one talks about the “mill” of the Krebs cycle of oxidation or about the mitochondria as “power plant” of the cell, it means that machinelike structures at the molecular level determine the order of enzyme reactions; similarly, it is a micromachine which transforms or translates the genetic code of DNA of the chromosomes into specific proteins and eventually into a complex organism.
Notwithstanding its success, the machine model of the organism has its difficulties and limitations.
First, there is the problem of the origin of the machine. Old Descartes did not have a problem because his animal machine was the creation of a divine watchmaker. But how do machines come about in a universe of undirected physico-chemical events? Clocks, steam engines and transistors do not grow by themselves in nature. Where do the infinitely more complicated living machines come from? We know, of course, the Darwinistic explanation; but a doubt remains, particularly in the physically minded; there remain questions not usually posed or answered in textbooks on evolution.
Secondly, there is the problem of regulation. To be sure, self- repairing machines are conceivable in terms of the modern theory of automata. The problem comes in with regulation and repair after arbitrary disturbances. Can a machine, say, an embryo or a brain, be programmed for regulation not after a certain disturbance or finite set of disturbances, but after disturbances of an indefinite number? The so-called Turing machine can, in principle, resolve even the most complex process into steps which, if their number is finite, can be reproduced by an automaton, However, the number of steps may be neither finite nor infinite, but “immense,” i.e., transcending the number of particles or possible events in the universe. Where does this leave the organism as machine or automaton? It is well-known that organic regulations of such sort were used by vitalists as proof that the organic machine is controlled and repaired by superphysical agents, so- called entelechies.
Even more important is a third question. The living organism is maintained in a continuous exchange of components; metabolism is a basic characteristic of living systems. We have, as it were, a machine composed of fuel spending itself continually and yet maintaining itself. Such machines do not exist in present-day technology. In other words: A machinelike structure of the organism cannot be the ultimate reason for the order of life processes because the machine itself is maintained in an ordered flow of processes. The primary order, therefore, must lie in the process itself.
Source: Bertalanffy Ludwig Von (1969), General System Theory: Foundations, Development, Applications, George Braziller Inc.; Revised edition.