ABSTRACT
In 1844, Jacob Henle and Carl Pfeufer founded the Zeitschrift für rationelle Medizin. The first issue contained a long essay in which Henle distinguished three approaches to medicine: a speculative or theoretical approach, strict empiricism, and rational medicine (a combination of theory and observation). In his essay, Henle was sharply critical of existing causal thinking in medicine. He wrote that typical etiological discussions were so fallacious that medicine appeared ridiculous in comparison to the exact sciences, and he continued:
This paragraph contains three different criticisms of existing causal thought in medicine and, by implication, three ideals that physicians should strive for in identifying causes. (1) In the first sentence Henle objected to accepting, as causes, factors that can have different effects or even no effect at all. Thus to be acceptable to Henle, a cause must always have the same effect; in other words it must be sufficient for its effect. (2) In the second sentence Henle objected to accepting, as causes, factors that need not be present for a given effect to occur (because the same effect could flow from other possible causes); in other words, he objects to factors whose absence does not insure the absence of the effect. Thus, to be acceptable to Henle, the absence of a cause must always accompany the absence of the effect; in other words, the cause must be necessary for its effect. In Henle’s view, only factors that are both sufficient and necessary should be accepted as causes in rational medicine.
