What are undesigned coincidences?

An undesigned coincidence is a particular shape of fit between texts: one account mentions a detail that is puzzling or incomplete, and another account, written for unrelated purposes and showing no awareness of the first, casually resolves it. When John's Gospel has Jesus ask Philip specifically where to buy bread, it never says why Philip. Luke notes the feeding happened near Bethsaida; and John, five chapters earlier and for an unrelated reason, mentions that Philip was "from Bethsaida." Lay the three side by side and the puzzle dissolves - yet no writer flags the link. Other cases interlock the Gospels with Acts through Herod's court (Joanna, wife of Herod's steward; Manaen, raised with Herod).

William Paley pioneered the method in 1790; John James Blunt coined the phrase in 1847; and the philosopher Lydia McGrew revived it in Hidden in Plain View (2017), framing it probabilistically: such interlocks are far more likely if the sources are well-informed and independent than if they are invented.

The sharpest objection, from the skeptic Richard Carrier, is literary dependence: if Luke copied Mark, apparent "coincidences" are just shared sources. That is partly right, and the weakest cases (like Mark's "green grass" and John's spring Passover) should be held loosely if John knew Mark. But a copyist who noticed a connection would state it; the strong cases do the opposite, burying the explaining detail in an unrelated context. Undesigned coincidences do not prove any event happened, still less a miracle - the manuscript case for accurate text is separate. What they establish is more modest and durable: these documents behave like independent, well-informed testimony to real events, not late legend or coordinated invention.