Proof

PROOF JOSEPH HERMAN" The question ofwhat constitutes confirmation of a scientific proposition belongs to the realm of epistemology which is only secondarily concerned with making sure that the laws ofscience reflect and predict what transpires in the animate and inanimate spheres external to humanity. Indeed, Poincar é held that such laws, like works of art, are free creations of the human mind, so that a rigorous demonstration has most to do with satisfying certain intellectual and, at times, aesthetic demands [1] . In what ensues I shall examine briefly some modes of proof operative in medical science. In the course of this examination it will, I hope, become clear that serendipity and intuition win the day over rigor—to which scientific endeavor can, only on rare occasions, aspire. Causality The most rigorous formulation of proof in medicine is given by Koch's postulates, the fulfillment of which enables the establishment of a causal association between an organism and a particular disease [2]. The high degree of specificity called for by the postulates is said to have influenced thinking in fields outside of the infectious disorders and to be applicable, after suitable adjustment, to cancer, nutritional deficiencies, allergy, and others [2]. However, in order to satisfy the first postulate—"The organism must be found in all cases of the disease in question"—there has to be an absolutely reliable means of diagnosing, say, tuberculosis before mycobacteria are isolated: something that, in a sense, begs the question. Moreover, the third postulate—"When the pure culture is inoculated into susceptible animals or man, it must reproduce the disease"—cannot be met if no animal model is available and there are no human volunteers. Thus, the postulates appear to come to grief because the criterion standard of diagnosis Correspondence: 24 Megadim Street, Y'fe Nof 96185 Jerusalem, Israel. *Department of Social Medicine, Family Practice Unit, Hebrew University, Hadassah Medical School.© 1997 by The University of Chicago. All rights reserved. 0031-5982/97/4002-0996$01.00 592 Joseph Herman ¦ Proof is a purely clinical one, with limited predictive value. Ancillary tests such as the staining ofsputum and gastricjuice samples, cultures, and guinea pig inoculation are designed to improve diagnostic accuracy. To allow proofof causality to rest on them is to be open to the charge of circular reasoning. In effect, Koch's postulates are no more than a schema for rigorous reflection on cause and effect. They have been criticized for taking no account of the host, be it laboratory animal or human being. Varying degrees ofresistance, nutrition, stress, and comorbidity are ignored, as are personality and the distinction between infection and disease [2] . Finally, the postulates , because they were enunciated before there were effective treatments for most bacterial diseases, do not admit the results of therapeutic trials as supporting evidence for infection. Addison 's Disease The ascription, in 1855, of weakness, hyperpigmentation, and nervous and mental irritability to disease of the supra-renal glands, mystery organs until that time [3] , must be considered one ofthe most astounding developments in the history of medicine. It might never have occurred were it not for Thomas Addison's abiding interest in dermatology, in which specialty he worked prior to beginning his association with Guy's Hospital [3]. The physicians of his day were no less astonished at what he achieved than we are at present, and one of them expressed the feeling as follows: We are told that in one case, which had baffled all investigation, Addison was called in, and after careful enquiry, stated positively that the patient suffered from a disease ofthese organs, which would before long prove fatal. This opinion was received with polite incredulity, but it wasjustified by the result, and the supra-renal capsules were found diseased. [4] The total number of patients Addison reviewed in his report on suprarenal disease was 11, and five have since been removed from the list as not representing instances ofAddison's disease [3] . Thus, six subjects on whom autopsies were performed form the basis ofan incredible piece ofinductive research enabling us to predict, after taking a history and performing a physical examination, the condition of two glands, generally weighing no more than five grams and being...