Do Two Agreeing Sources Count as Two Pieces of Evidence?

Two news sites both report that a company will release a product on Friday, which can look like two confirmations. But if both articles rewrite the same company press release, they are one piece of information travelling along two publication routes, not two independent bodies of evidence.

The epistemology of testimony asks why we can gain knowledge from what other people tell us. A reductionist tradition, often traced to Hume, stresses that a hearer needs positive reasons for treating a speaker as reliable. Non-reductionists associated with Thomas Reid and, later, C. A. J. Coady argue that testimony can have defeasible initial credibility when there is no reason to distrust it. Despite their disagreement, neither position makes repetition automatically stronger evidence. If the second reporter merely copies the first source, there is no new observation, method or responsible judgement.

Genuine corroboration comes from partly independent informational paths. One reporter might verify the date in company documents while another checks with a retailer that has received an invitation. Both can still be wrong, but they do not share the entire error pathway as copied press releases do. Independence is also a matter of degree: reporters may speak to different people while relying on the same faulty database.

My view is that public information should be assessed by counting traceable, independent chains of verification, not webpages. More sources add evidential weight only when they contribute new observation, a different method or separate responsibility for judgement. When a common origin is hidden, apparent consensus can create false certainty.

https://plato.stanford.edu/entries/testimony-episprob/

https://plato.stanford.edu/entries/epistemology-social/