A scientist who wishes to keep his friends and not add to the number of his enemies must not be forever scoffing and criticizing and so earn a reputation for habitual disbelief; but he owes it to his profession not to acquiesce in or appear to condone folly, superstition or demonstrably unsound belief. The recognition and castigation of folly will not win him friends, but it may gain him some respect.
Over a period of years I have collected a little treasury of more or less fallacious beliefs, and a discussion of some of these will help to exemplify criticisms of the kind I think just.
How often has it not been contemptuously said that "modern medicine cannot even cure the common cold"? What is offensive here is not the statement's falsity (it is true) but its implication: is it not pointless to pour billions of dollars into cancer research when modern medicine... and so on. What is wrong here is the almost universally held belief that clinically mild diseases have simple causes while grave diseases are deeply complex and are proportionately difficult to discern the causes of or to cure. There is no truth in either; a common cold, caused by one or more of a multiplicity of upper respiratory viruses and with an overlay of allergic reactivity, is an extremely complex ailment; so is eczema, most forms of which are baffling still. On the other hand, some very grave diseases such as
phenylketonuria have relatively simple origins; some can be prevented, as phenylketonuria can be, or cured, as so many bacterial infections can be. Some forms of cancer are simple in origin and can be circumvented — for
example, the cancers caused by smoking and by certain industrial chemicals. Indeed, good judges have put the proportion of all cancers {49} caused by extrinsic agents as high as 80 percent.
Another declaration of the same genre as the one about the common cold is that "cancer is a disease of civilization"
— a seemingly natural inference from the fact that cancer is much more widely prevalent in the industrialized countries of the Western world than in the developing nations. But it is second nature to people familiar with
demography or epidemiology to ask if the populations being compared are genuinely comparable, and here they are not. It is his relatively high expectation of life — of his not dying, that is to say, for other reasons — that confers upon Western man his relatively high expectation of contracting cancer — a disease of middle or later life — so the inference is unsound. Comparisons of mortality are valid only if populations are standardized with respect to
variables such as their age compositions, with allowance, too, for differences in skills of diagnosis.
Another way in which a scientist can lose friends is to call attention to the tricks that selective memory can play upon judgment. "Three times, no less, I dreamed of Cousin Winifred, and on the very next day she rang me up. If that
doesn't prove that dreams can foretell the future, then I'm sure I don't know what does." But, the young scientist expostulates, on how many occasions did you dream of Cousin Winifred without a subsequent telephone call? And is it not a fact that she rings up almost every day? We remember only the striking conjunctions; there is no incentive to remember occasions when misfortunes come singly or in pairs, and not in threes (or whatever other number superstition fixes on). Seeing an example of bad driving, a man of a certain temperament will remark it and
remember it only if the car is driven by a woman — and thus he convinces himself of women's lesser skill without realizing his own errors of judgment.
Writing on the same subject as this, the endocrinologist Dr. Dwight Ingle has recounted the following variant of a chestnut of immemorial origin:
PSYCHIATRIST: Why do you flail your arms around like that?
PATIENT: To keep the wild elephants at bay.
PSYCHIATRIST: But there aren't any wild elephants here.
PATIENT: That's right. Effective, isn't it? {50}
Post hoc, ergo propter hoc has many devotees, and some of them, I fear, have been scientists. Classical
embryologists, for example, were at one time wont to believe that a complete anatomical record of antecedent states provided causes enough to explain development.
Superstitions are not so easy to cope with. Probably it is better not to try to reason with astrological predictions, but it may be worthwhile just once to call attention to the extreme a priori unlikelihood of their being true, and point to the lack of any convincing evidence that they are so. But perhaps after all it is best to let sleeping unicorns lie — I myself have for some time past abstained from discussing spoon bending or other manifestations of "psychokinesis."
Wise scientists and medical men take some pains to guard against the dangers arising out of a predilection for getting one experimental result rather than another. If an experiment cannot be fully controlled, matters are so arranged that uncontrollable sources of error tell, if anything, against the hypothesis one would like to see
corroborated. Moreover even the most experienced and honorable clinicians fall in readily with the drill of "double-blind trials" — those in which neither physician nor patient knows whether the patient has received a supposedly efficacious medicament or a placebo made up to look and taste like it. If strictly carried out, and if the member of the team responsible for it has not lost the key of the code, evaluation of the treatment can be carried out on a genuinely objective basis, uninfluenced by the physician's wishes, or the patient's.
Exaggerated claims for the efficacy of a medicament are very seldom the consequence of any intention to deceive;
they are usually the outcome of a kindly conspiracy in which everybody has the very best intentions. The patient wants to get well, his physician wants to have made him better, and the pharmaceutical company would like to have put it into the physician's power to have made him so. The controlled clinical trial is an attempt to avoid being taken in by this conspiracy of good will.
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