In medicine, etiology refers to the<unk> or<unk>  of diseases or pathologies. Where no etiology can be ascertained, the disorder is said to be idiopathic. Traditional accounts of the<unk>  of disease may point to the "evil eye". The Ancient Roman scholar Marcus Terentius Varro put forward early ideas about microorganisms in a 1st-century BC book titled On Agriculture. Medieval thinking on the etiology of disease showed the influence of Galen and of Hippocrates. Medieval European doctors generally held the view that disease was related to the air and adopted a miasmatic approach to disease etiology. Etiological discovery in medicine has a history in Robert Koch's demonstration that species of the pathogenic bacteria Mycobacterium tuberculosis<unk>  the disease tuberculosis; Bacillus anthracis<unk>  anthrax, and Vibrio cholerae<unk>  cholera. This line of thinking and evidence is summarized in Koch's postulates. But proof of<unk> tion in infectious diseases is limited to individual<unk> s that provide experimental evidence of etiology. In epidemiology, several lines of evidence together are required to for<unk> l inference. Austin Bradford Hill demonstrated a<unk> l relationship between tobacco smoking and lung cancer, and summarized the line of reasoning in the Bradford Hill criteria, a group of nine principles to establish epidemiological<unk> tion. This idea of<unk> lity was later used in a proposal for a Unified concept of<unk> tion.
Cause 
Outline of health
Component causes
The Soul of Medicine
Mental event
Uniject
Fitness 
Social 