Start here
Four cases to begin with.
Four selected cases show different ways knowledge changes. Read them in order, or begin with the case that interests you.
How to read a case
Compare the earlier claim with the current understanding. Then read why it changed and what each source establishes. The questions below help you check the limits of the account.
The first two cases come from the core catalogue: scientific claims once reasonably accepted. The last two come from Institutional Beliefs: claims that shaped institutional practice, including claims that relevant experts already contested.
Better measurement
Counting human chromosomes
Core catalogue
Improved chromosome preparations made an accepted count possible to check again.
A question to read withWhat made the new count more reliable, and which cells does it describe?
A new explanation, with limits
Peptic ulcers
Core catalogue
The case sets out the evidence for H. pylori and NSAIDs, while keeping the role of stress in context.
A question to read withHow do the source notes support the main causes without claiming one cause explains every ulcer?
Professional guidance changes
Routine oxygen for heart attacks
Institutional Beliefs
Follow a recommendation from its original evidence level through clinical trials to revised guidance.
A question to read withWhich patients did the recommendation concern, and what did the institution actually change?
When challenge is suppressed
Lysenkoist heredity
Institutional Beliefs
Read how staffing, teaching and research controls gave a doctrine authority, then compare the institutional responses.
A question to read withWhich consequences are directly documented, and which wider historical outcomes require more cautious attribution?
Keep exploring
These four cases are an introduction, rather than a ranking or a representative sample. Explore more cases, or read how they are selected and sourced.