Readers may be familiar with the Seinfeld television show episode where the George Costanza character resolves to do the opposite of everything he normally does. The idea actually has a legitimate pedigree, at least with regard to ancient medical science.
Arguably the most influential writer of late antiquity was the physician and philosopher Galen of Pergamum. His life spanned the years 129 to about 215 A.D., but we cannot be certain of these precise dates. Besides being an accomplished surgeon and philosopher, he also was among the most fecund of writers in any discipline; his collected works today fill over twenty-five thick volumes.
He was not an arid speculator; he believed that real knowledge could only be gained by blending rigorous experience grafted onto a solid theoretical framework. In the opening paragraph of his On Medical Experience (De experientia), he cautions us:
When I take as my standard the opinion held by the most skillful and wisest doctors and the best philosophers of the past, I say: ‘the art of healing was originally invented and discovered by logos [reason] in conjunction with experience. And today also it can be practised excellently and done well by one who employs both of these methods.
The only sure way to gain knowledge, then, was by relying both on experience and “reason.” Experience without reason is disorganized and diffuse; and reason without experience is lacking in depth and realism. The two principles complement each other and fail in the absence of the other. When it came to the human body, function followed structure; we cannot hope to understand the purpose behind some organ without having a detailed knowledge of its construction. The purpose of medicine was to heal, or to restore the body to its natural state; causality prevailed, in that there was an explanation for every event. Things did not just happen: behind everything lay a logical explanation.
One of his primary principles of treatment was the idea of “opposites.” What Galen meant by this was that the body’s natural state could be restored by presenting the body with some “opposite” principle than what it was currently exposed to. Such opposites could take the form of food, drink, materia medica (medicines), or any other type of therapy that was the direct antithesis of what was negatively affecting the health. According to him, there were five “classes” of disorder: size, conformation, number, position, and break in continuity.
As the title of this article suggests, one of Galen’s most interesting idea was the premise that opposites neutralize each other to produce a restorative balance. A knowledgeable doctor would be able to make use of this principle to effect consistent cures. He explains further:
In those affected in respect of conformation, we must lead them back to forms in accord with nature by emptying what has been filled and filling what has been emptied, by opening up blockages, by bringing together what has been opened up, and by turning toward the opposite what has been closed and condensed, opening up some and rarefying others. It is the same even in disease relating to position; the objective is to effect a return to an accord with nature. In disease relating to dissolution of continuity, it is to bring about a binding together of what has been separated.
But how is this done, precisely? How do we bring an “opposite” to bear? Galen provides us specific examples. A dislocated shoulder can be brought back into alignment by the right counterforce applied to the muscles and joints. “It is impossible to bring about reduction without countertension,” he reminds us. I remember a similar example from my own experience. When I was a freshman in college some years ago, I suffered a collapsed lung due to spontaneous pneumothorax. The first attempted remedy of the physician was to attempt to re-inflate the lung using negative pressure; this was done by removing air from the pleural cavity. (When this was not successful, surgery was then necessary, but only as a last resort).
So this was Galen’s basic theory of opposites. Reckless generalizations are always hazardous in such matters, and the idea does not work in every situation. But we may state the following with confidence: if something is wrong, it is useful to try to attempt an opposite principle to counteract it. Implicit in this principle is the concept of making bold adjustments. Small changes are usually inadequate; we must be bold in restoring things to their proper balance. Sometimes we must shock our system back into health by doing the opposite of what it has become accustomed to.
To cure a major problem, we must be prepared to use a countervailing principle of equal or greater magnitude.
To learn more about similar ideas, be sure to read On Duties.
 On Medical Experience, in Walzer and Frede, Three Treatises, 49.
 Constitution on the Art of Medicine, 5. (Trans. by Ian Johnston)
 Id at 13.