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'Science' in the Social Sciences

4. Causal Reasoning

The same holds true for causal reasoning about states of the organism, an important feature of epidemiological and biostatistical reasoning. Nonetheless, as we learn from Turners’s (1997) illuminating discussion of the history of theories of cholera (see also Hughes and Sharrock, 2007:174-75), deriving etiological theories from statistical materials alone has its hazards.

    Image of British epidemiologist William Farr  

William Farr (1807-1883)

William Farr studied cholera and its concomitants.
Farr’s biostatistical ‘law’ asserted that halving the elevation above sea level in areas where people lived would double the mortality rate for cholera.

Enter John Snow, now known as the first epidemiologist.
During an outbreak of cholera in London in 1854, Snow plotted on a map the location of all the cases he learned of. Water in that part of London was pumped from wells located in the various neighborhoods. Snow's map revealed a close association between the density of cholera cases and a single well located on Broad Street. Removing the pump handle of the Broad Street well put an end to the epidemic. This despite the fact that the infectious agent that causes cholera was not clearly recognized until 1905.

Snow's painstaking research showed that what Farr had derived from his statistical distributions culminated in a mistake: his so-called ‘law’ held only for the 1849 epidemic, and pointed toward the wrong hypothesis: Snow concluded that the relationship which Farr had described was “the result of coincidental circumstances specific to that epidemic” (Hughes and Sharrock, 2007:174-75). Snow propounded the thesis that cholera is a water-borne disease.

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Turner, S. (1997). Net effects: a short history. In V. R. McKim & S. P. Turner (Eds.), Causality in crisis? Statistical methods and the search for causal knowledge in the social sciences. Indiana: University of Notre Dame Press.
Hughes, John A. & W. W. Sharrock (2007). Theory and methods in sociology: an introduction to sociological thinking and practice. Basingstoke, UK and N.Y.: Palgrave Macmillan.