Why does responsible journalism insist on at least two independent sources before publishing?

One source can be wrong, biased or deliberately feeding you a false story — two independent accounts that agree turn a claim into corroborated evidence.

A single source has no check on it. The person may be mistaken, may have an agenda, or may be planting a story to damage someone. If a second, independent source describes the same course of events the same way, the odds that both are wrong or both are lying in the same direction drop sharply.

"Independent" is the load-bearing word: two outlets that both copied the same press release are really one source wearing two hats. Genuine corroboration means the accounts trace back to separate origins.

Tip: This is also why "a leaked document says…" is weak on its own — a document plus a person who can vouch for its context is stronger than either alone.