Inferring and Explaining

61 milk and miasma accounts of childbed fever. Miasma, or “epidemic infuences,” has a tough time explaining observations two, three, and four (e 2 , e 3 , and e 4 ). It seemed obvious that the causal origin of the epidemic must lie in some way with diferences between the two mater- nity divisions. Most philosophers of my generation know of Semmelweis’s story because of a very infuential little textbook: Philosophy of Natural Science by Carl Hempel, one of the most sophisticated pro- ponents of the “pretty picture of science.” He interprets Semmelweis’s careful procedure as one of conducting a series of miniexperiments to rule out possible causal diferences between the two divisions. As long as we remember that experiments are simply a systematic way of gathering relevant new data and then reassess- ing the explanatory virtues of the competing hypotheses, this is a very useful way of inter- preting Semmelweis’s method. One of the minor diferences between the divisions was the position of the woman at birth: “A new idea was suggested to Semmel- weis by the observation that in the First Divi- sion the women were delivered lying on their backs; in the Second Division, they delivered on their sides. Tough he thought it unlikely, he decided, ‘like a drowning man clutching at a straw,’ to test whether this diference in pro- cedure was signifcant. He introduced the use of the lateral position in the First Division, but again, the mortality remained unafected.” 4 We are ofered a new rival explanation: t 4 . Delivery in the supine position causes childbed fever. Te new data from Semmelweis’s miniexperi- ment, however, drops this hypothesis way down on the rank ordering. semmelweIs and ChIldBed feVer e 7 . Changing to the lateral position for deliv- ery in the First Division made no diference in the mortality rates. Another interesting diference had to dowith the administering of the Catholic last rights, of all things. Various psychological explanations were attempted. One of them noted that the First Division was so arranged that a priest bearing the last sacrament to a dying woman had to pass through fve wards before reaching the sickroom beyond: the appearance of the priest, preceded by an attendant ringing a bell, was held to have a terrifying and debilitating efect upon the patients in the wards and thus to make themmore likely victims of childbed fever. In the Second Division, this adverse factor was absent, since the priest had direct access to the sickroom. Semmelweis decided to test this conjecture. He persuaded the priest to come by a roundabout route andwithout ringing of the bell, in order to reach the sick chamber silently and unob- served. But the mortality in the First Division did not decrease. 5 Again, we have a new rival explanation: t 5 . The “terrifying and debilitating” efect of the deathbed priest’s appearance was caus- ing childbed fever. But the experimental new data makes that a very poor explanation.