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8.3: Good Arguments

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    127488
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    A historical example

    An important example of excellent reasoning can be found in the case of the medical advances of the Nineteenth Century physician, Ignaz Semmelweis.  Semmelweis was an obstetrician at the Vienna General Hospital.  Built on the foundation of a poor house, and opened in 1784, the General Hospital is still operating today.  Semmelweis, during his tenure as assistant to the head of one of two maternity clinics, noticed something very disturbing.  The hospital had two clinics, separated only by a shared anteroom, known as the First and the Second Clinics.  The mortality rate for mothers delivering babies in the First Clinic, however, was nearly three times as bad as the mortality for mothers in the Second Clinic (9.9 % average versus 3.4% average).  The same was true for the babies born in the clinics:  the mortality rate in the First Clinic was 6.1% versus 2.1% at the Second Clinic. In nearly all these cases, the deaths were caused by what appeared to be the same illness, commonly called “childbed fever”.  Worse, these numbers actually understated the mortality rate of the First Clinic, because sometimes very ill patients were transferred to the general treatment portion of the hospital, and when they died, their death was counted as part of the mortality rate of the general hospital, not of the First Clinic.

    Semmelweis set about trying to determine why the First Clinic had the higher mortality rate.  He considered a number of hypotheses, many of which were suggested by or believed by other doctors.

    One hypothesis was that cosmic-atmospheric-terrestrial influences caused childbed fever.  The idea here was that some kind of feature of the atmosphere would cause the disease.  But, Semmelweis observed, the First and Second Clinics were very close to each other, had similar ventilation, and shared a common anteroom.  So, they had similar atmospheric conditions.  He reasoned:  If childbed fever is caused by cosmic-atmospheric-terrestrial influences, then the mortality rate would be similar in the First and Second Clinics.  But the mortality rate was not similar in the First and Second Clinics.  So, the childbed fever was not caused by cosmic-atmospheric-terrestrial influences.

    Another hypothesis was that overcrowding caused the childbed fever.  But, if overcrowding caused the childbed fever, then the more crowded of the two clinics should have the higher mortality rate.  But, the Second Clinic was more crowded (in part because, aware of its lower mortality rate, mothers fought desperately to be put there instead of in the First Clinic).  It did not have a higher mortality rate.  So, the childbed fever was not caused by overcrowding.

    Another hypothesis was that fear caused the childbed fever.  In the Second Clinic, the priest delivering last rites could walk directly to a dying patient’s room.  For reasons of the layout of the rooms, the priest delivering last rites in the First Clinic walked by all the rooms, ringing a bell announcing his approach.  This frightened patients; they could not tell if the priest was coming for them.  Semmelweis arranged a different route for the priest and asked him to silence his bell.  He reasoned:  if the higher rate of childbed fever was caused by fear of death resulting from the priest’s approach, then the rate of childbed fever should decline if people could not tell when the priest was coming to the Clinic.  But it was not the case that the rate of childbed fever declined when people could not tell if the priest was coming to the First Clinic.  So, the higher rate of childbed fever in the First Clinic was not caused by fear of death resulting from the priest’s approach.

    In the First Clinic, male doctors were trained; this was not true in the Second Clinic.  These male doctors performed autopsies across the hall from the clinic, before delivering babies.  Semmelweis knew of a doctor who cut himself while performing an autopsy, and who then died a terrible death not unlike that of the mothers who died of childbed fever.  Semmelweis formed a hypothesis.  The childbed fever was caused by something on the hands of the doctors, something that they picked up from corpses during autopsies, but that infected the women and infants.  He reasoned that:  if the fever was caused by cadaveric matter on the hands of the doctors, then the mortality rate would drop when doctors washed their hands with chlorinated water before delivering babies.  He forced the doctors to do this.  The result was that the mortality rate dropped to a rate below that even of the Second Clinic.

    Semmelweis concluded that the best explanation of the higher mortality rate was this “cadaveric matter” on the hands of doctors.  He was the first person to see that washing of hands with sterilizing cleaners would save thousands of lives.  It is hard to overstate how important this contribution is to human well being.  Semmelweis’s fine reasoning deserves our endless respect and gratitude.

    But how can we be sure his reasoning was good?  Semmelweis was essentially considering a series of arguments.  Let us turn to the question:  how shall we evaluate arguments?


    8.3: Good Arguments is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

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