What is disease? The whole philosophy of drug medication or of Hygienic care turns on this single question. It is quite clear that until medical men can solve this problem--what is disease--medical science cannot advance. It must remain a science without a system, a superstructure standing on nothing. Although the minds of medical men have given origin to diverse theories of the nature and cause of disease, they have all revolved around a common center. Disease has been regarded as a positive and organized entity which attacks the body from without.
Our forefathers would conjure up for themselves some hideous monster and imagine him dancing around, peeping in windows, slipping in at doors and ready to pounce upon them at any minute. They were entirely unarmed; there was no protection. Although this ancient conception of disease has faded somewhat, it is not entirely dead. From the time of the incantations and charms of the era of the magician down to the present time, that mysterious imaginary monster, disease, has been the thing aimed at; and remedies supposed to possess curative virtues have been employed with which to combat, expel and kill it. Whatsoever was done, whether by ceremonies or by drugging, the sick have had faith in the "power to cure" possessed by the act performed or by the drug taken. If they failed to recover under the treatment, this did not lessen their faith in "nature's remedies." They thought only that they had failed to find one suitable to their case. Hence it is and has been that invalids have always been and are perpetually and continually resorting to one thing after another to cure them of their maladies.
Whether the people and their physicians really imagine that disease is a thing--an entity--destroying the patient in like manner as a worm gnawing at its root destroys a plant and that, consequently, the disease must be destroyed as we would destroy the worm, it is certain that their treatment, when ill, is directed to this end. From the dawn of human history to the present, all magic and all medication has been employed, no matter what the theory, upon the assumption that disease is a positive organized force that has attacked the body. Accordingly, a power outside the living organism has been sought after and used for the purpose of curing disease.
We regard an understanding of the essential nature of disease as not only important to the establishment of a successful mode of caring for the sick, but as essential to the establishment of a true science of life. The natural termination and course of a so-called disease can be known and understood only by the man who observes its progress from beginning to end without interfering in any way with its processes. From Hippocrates down to the present no physician who gives drugs has ever studied the natural history of disease. How can a man tell the natural history of anything who has never seen it in its natural relations? How are physicians to understand the nature of disease so long as they continue to meddle with it at every stage of its progress?
One difficulty in defining disease is that it is a generic term that covers a rather wide variety of phenomena, some of them directly opposite to others. For example, there may be violent action or there may be a complete loss of power of action. So long as the word disease is employed as a blanket term covering so many and opposite phenomena, a satisfactory definition is not possible. The medical dictionary defines disease as "a departure from the normal." It is obvious that such a definition also covers a wide variety of phenomena, often of opposite character. Other than this, it is unsatisfactory for the reason that it fails to define the normal. How can we define a departure from the normal until we know what is normal? Under this definition a child born with six fingers on one hand would be diseased; yet it is quite obvious that as much as a departure from the normal as the six fingers would be, this is something entirely different from pneumonia or typhoid fever. We are much in need of a terminology that will clearly distinguish between the various kinds of departures from the normal.
A large part, if not all, of the physical world is composed of continua, by which is meant that a continuum is a heterogeneous unity, each point of which differs from all the other adjacent points, but differs from them by such subtle gradations in any particular quality that there exists no boundaries within the unity, but which can be divided into parts only by imaginary and arbitrary boundaries. If we think of temperature and the wide range between the lowest and highest possible temperatures and consider for a minute the fact that there is no point on the thermometer where we can place our finger and say with certainty that precisely at this point cold ends and heat begins, or vice versa, and that all the little markings, crude and gross though they be, on the thermometer by which we measure degrees of temperature, do not represent actual divisions of temperature, but arbitrary and imaginary divisions, we get an idea of one continuum.
We can think of health and disease also as a continuum. Comparing these two phases of life (the state of being alive) to temperature, let health represent heat and disease represent cold. At what precise point on our vitometer can we place the thin edge of a knife and say with certainty that here health ends and disease beings? The two states shade imperceptibly into each other as do the colors of the rainbow. This is not to say that health and disease are the same thing, any more than heat and cold are the same thing, but that, just as heat and cold are two phases of the same thing (temperature), so health and disease are two phases of the same thing (life) and that, just as heat and cold merge imperceptibly into each other, so health and disease also merge imperceptibly into one another.
In truth, many aspects (stages) of disease are continua, existing in such subtle gradations and in such varied degrees of abstractness that the differentiations made by pathologists in the course of their analyses and the terms they employ as symbols of their analytical divisions reflect only very roughly the pathological situation that exists in reality. All the phenomena of health and disease proceed from the living system. Disease is no more an extra-body entity than is health. Both health and disease readily change under changed conditions, according as the body is related to the changed circumstances. Disease is a vital struggle (biogony) to remove offending substances (toxins) and repair damages. It is a modification, for the most part, of the regular, orderly processes of life designed to accomplish some unusual end--the removal of toxins engendered or taken in from without. Pathology, in this view, is the dramatic exaggeration or diminution of normal processes--it is not healthy action, but is health-restoring in effect.