The Cancer J. 7: 2:48-49,1994.

Georges Canguilhem

The normal and the pathological are two pillars of medicine. The normal is symptomless and is not perceived. Only the pathological draws our attention and through disease we appreciate the normal. Nevertheless, the pathological is defined as a deviation from normal. What is then normal and when does a deviation from it becomes pathological? This profound question was addressed to by the greatest minds of modern medicine and their views were summarized in 1943 by the philosopher and physician Georges Canguilhem (1).

This fine treatise is an important contribution to the philosophy of modern medicine, along with Fleck's philosophical work that was mentioned previously (2-4). Both philosophers refrain from interpreting pathology in the absolute sense. Canguilhem maintains that the definition of normal and pathological depends upon the circumstances in which they are observed. According to Fleck, disease is not an absolute entity. Diseases do not exist in nature and are constructed by physicians for didactic purposes. Both philosophers are regarded here as medical relativists.

Claude Bernard

Bernard considered medicine as science of diseases, and physiology as science of life. "Physiology and pathology are intermingled and are essentially one and the same thing" (p.67) (The forthcoming page numbers refer to the English translation of Canguilhem's work (1))."Every disease has a corresponding normal function of which it is only the disturbed, exaggerated, diminished or obliterated expression." (p.68). Bernard maintains that the transition from normal to the pathological proceeds in a continuous and reversible fashion, e.g., the blood sugar level, that changes smoothly from normo- to hyper- or hypo- glycemia. Pathology may therefore be expressed quantitatively. According to Bernard: "there is no case where disease would have produced new conditions, a complete change of the scene, or some new and special products." (p. 71). Bernard's approach suffices for describing metabolic and hormonal disorders, and fails in diseases whose manifestations are discontinuous and do not proceed through hypo- normo- and hyper- states, e.g., infectious or neurological.

Rene Leriche pointed out that although the normal state precedes disease, knowledge of the normal is triggered by disease. "At every moment there lie within us many more physiological possibilities than physiology would tell us about. But it takes disease to reveal them." (p.100). Or as Canguilhem puts it: "Disease reveals normal functions to us at the precise moment when it deprives us of their exercise." (p. 101).

What is Normal?

The normal can be defined either qualitatively, e.g., normal is that which is such that it ought to be, or quantitatively, e.g., normal is that which is observed in the majority of cases. (p.125). To modern medicine both concepts are equivalent. The "qualitative normal" is estimated statistically and equals the population average which according to epidemiology is the best estimate of the normal. Epidemiology regards deviations from the normal as random and meaningless, which contradicts clinical experience according to which deviations from the average are neither random nor meaningless. Take for instance the normal pulse rate of 50 beats/min. observed in an athlete. It deviates significantly from the population average and the deviation is not random.

Epidemiology tries to obviate this difficulty by grouping individuals into functional classes, each with its own normal average. This may be appropriate for discrete variables, yet fails when applied to variables that change smoothly in a continuous fashion, e.g., blood glucose. What is a normal blood sugar level? A seemingly innocent question that spurred heated debates among biochemists and still remains unresolved. It illustrates the conceptual confusion of epidemiology (5-9). From the clinical point of view the average is not normal. The normal is meaningful only in the context of the individual.


The "normal" concept is ambiguous and has two meanings. On one hand it describes the condition of the individual, or his state, while on the other it relates to the quality or value of this state. We shall therefore reserve the word "norm" for the first and apply "normal" when evaluating the norm. The organism maintains its norm actively and adjusts it continually. Among other, the norm maintains an equilibrium known as Homeostasis. Unlike the equilibrium of a chemical reaction that is established passively, homeostasis is maintained actively. From the philosophical point of view, since maintaining its norm actively the organism is normative.

"Normative in the fullest sense of the word, is that which establishes norms." (p.127). Homeostasis is maintained even if the organism undergoes conspicuous changes, e.g., in the growing child, when growth proceeds from one homeostasis state to another, or from one norm to another. The "decision" of the organism what norm to adopt, is regarded here as a normative activity.

Greek medicine regarded this normative capacity as healing force of nature, or vis medicatrix naturae. Canon called it "Wisdom of the Body" (10). Normative activity controls healing processes in the organism, and according to Guyenot the organism "is the first among physicians" (p. 130), to which Canguilhem adds: "It is life itself and not medical judgment which makes the biological normal a concept of value and not a concept of statistical reality." (p. 131). Yet even this definition of the normal is incomplete, since the normative activity of the organism depends also on the environment. "Taken separately, the living being and his environment are not normal: it is their relationship that makes them such. (p. 143)

The survival of the best fitting norm

Normative activity is essential for the organism's survival in the hostile environment. According to the theory of evolution, from generation to generation organisms became better adapted to their environment. Those less adapted were eliminated leaving behind the better adapted. From the medical point of view, environmental threat is a noxa that triggers in the organism a strategy to evade it or to repair its damage. The strategies are normative and they evolved throughout the ages. From generation to generation they became more efficient. According to Darwin's theory, today's organisms are equipped with the best strategies to deal with noxae, otherwise they would not have survived (11). Guyenot's statement that the organism "is the first among physicians" may be regarded as corollary of Darwin's theory.

Health and disease

The interaction between a noxa and protective strategies in the organism is manifested as disease (11). Some phenomena observed in a disease are contributed by noxa, the rest are strategies mobilized by the organism representing its Normativity. During transition from health to disease the organism is not dragged by the disease passively, rather it chooses its most adequate norm under the given circumstances. Some functions change while other remain at their physiological level. According to Goldstein: "Disease is not merely the disappearance of a physiological order but appearance of a new vital order" (p. 193). "Disease is a positive, innovative experience in the living being and not just a fact of decrease or increase." . . . "Disease is not a variation on the dimension of health; it is a new dimension of life." (p. 186), and "the pathological cannot be linearly deduced from the normal." (p. 190).

A myocardial infarction reduces the normative capacity of the patient since his activities are reduced. According to Goldstein "The sick man is not abnormal because the absence of a norm but because of his incapacity to be normative.". . . "Disease is a narrowed mode of life, lacking in creative generosity because lacking in boldness, it is nevertheless true that for the individual, disease is a new life" {p.188). "Pathological phenomena are the expression of the fact that the normal relationships between organism and environment have been changed through the change of the organism."

Normativity operates in health as well as in disease. In Canguilhem's words: "being healthy and being normal are not altogether equivalent since the pathological is one kind of normal. Being healthy means being not only normal in a given situation but also normative in this and other eventual situations. What characterizes health is the possibility of transcending the norm" . . . "Health is a margin of tolerance for the inconsistencies of the environment" (p. 197). "To be in a good health means being able to fall sick and recover, it is a biological luxury". "Inversely, disease is characterized by the fact that it is a reduction in the margin of tolerance for the environment's inconsistencies." (p.199).

The relativity of the norm and the normal

After an heart attack is cured, the organism creates a new norm and its normative potential is reduced. "Cure" according to Goldstein "can just as well be interpreted as a change from one arrangement to another."(p. 190). "Being well means to be capable of ordered behavior which may prevail in spite of the impossibility of certain performances which were formerly possible. But the new state of health is not the same as the old one" . . .it is " a new individual norm " (p. 194).

"The fundamental biological fact that life does not recognize reversibility." says Canguilhem, " But if life does not admit of re-establishments, it does admit repairs which are really physiological innovations (p. 196). Life has a "boundless capacity to institute new biological norms." "The pathological must be understood as one type of normal, as the abnormal is not what is not normal, but what constitutes another normal." (p. 203). "The healthy organism is characterized by the tendency to face new situations and institute new norms (p. 204).


Since the ultimate goal of the organism is to preserve itself, it selects the norms that maximize its life preserving potential. The organism thrives to attain the fittest state under the given circumstances, and is therefore "the first among physicians" (Guyenot). Normativity is subdued to the self preservation principle and was selected therefore during evolution of species. The preservation principle ought to be considered during the interpretation of disease. According to Schwarz: "We grasp the meaning of our own organization in its tendency to preserve itself." (p.217). Life preservation is the most important criterion for distinguishing between normal and pathological. Treatment should therefore designed so as to boost Normativity in the right direction. Figuratively speaking, during treatment planning, the physician should consult the "wisdom of the body" how to assist the healing force of nature.

Theory of medicine

The philosophies of Canguilhem and Fleck provide the foundation for a theory of medicine that explores Normativity for the patient's benefit. The theory of medicine will soon be equipped with its own mathematics, Chaos (13-17). The mathematics of Chaos is suitable for describing complex non-linear phenomena that operate in the organism. The norm, is represented in Chaos by a strange attractor. The change of the norm observed in disease is represented by a transition from one attractor to another. Normativity means the selection of a strange attractor that maximizes the life preserving principle. . . Medical science is dawning!


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