Most diseases improve on their own regardless of what treatment happened nearby

Evidence

In fact, in the vast majority of diseases, at least a temporary improvement occurs at some point on its own. A person who happens to have just performed a rain dance at that time cannot claim to have cured the patient. The same applies if this rain dance took place in close temporal connection with a serious medical therapy, which could also have caused the improvement. — Holm Gero Hümmler, Ulrike Schiesser, Fact and Prejudice, 723

Categorization

• XREF: Connects to the placebo-effects and self-deception mechanisms referenced from the book’s own Chap. 2; also parallels the Milgrom trade-institution material about observed correlation not proving causation. — connects to: The sick are not necessarily healthier than the normal
• ADDENDUM: Relevant to the sacrifice piece — correlation arguments are used to credit causal agency to rituals (rain dances, sacrifices) that merely coincide with outcomes.

Related

• The sick are not necessarily healthier than the normal (similarity 0.90)