Methodological insights

In some way every biomedical researcher is searching for a kind of ultimate explanation of disease. So, we have been told that all cancers were due to mutations in p53 (some years ago), then it was the turn of epigenetics, and so on. It seems
that looking for a single and simple explanation of things—and an ensuing unambiguous classification— is inherent in human psychology. However, we should also be aware that at least sometimes it is not possible to find such an explanation and such a classification. For example, people have struggled for years but still an unambiguous
classification of viruses is not available.2 When we adopt a classification of disease (for example, International Classification of Diseases, tenth revision, ICD-10), or when we refer to the diagnostic criteria for disease, or when we think
of causes, we usually imply that such activities are based on unequivocal criteria that sharply distinguish one disease from another one, or that relate a cause to its effect. This is very clear in the paradigm of ‘‘necessary and sufficient’’ causes.
However, reality is very far from such interpretation.....

Vineis P., Methodological insights: fuzzy sets in medicine
doi:10.1136/jech.2007.063644
J. Epidemiol. Community Health 2008;62;273-278
http://jech.bmj.com/cgi/content/full/62/3/273

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source: British Medical Journal
http://jech.bmj.com/cgi/reprint/62/3/273