Did Jesus appear to 500 witnesses?

Yes - and remarkably early. In 1 Corinthians 15, written around AD 55, Paul recites something he says he 'received' and 'delivered': 'that Christ died for our sins... that he was buried, that he was raised on the third day... and that he appeared to Cephas, then to the twelve' — then to more than five hundred at once, to James, and last to Paul himself. The vocabulary and the Aramaic name 'Cephas' mark it as a formula older than the letter: a creed the earliest believers were already confessing.

How early? Paul's own timeline supplies the answer. Within a few years of his conversion he met Cephas and James in Jerusalem — two of the named witnesses. So the tradition predates his receiving it, pushing its origin to within roughly two to five years of the crucifixion. This is not apologetic special pleading: the atheist scholar Gerd Lüdemann dates its elements 'not later than three years' after the cross.

That window is too narrow for legend to have done its slow work, and named, living witnesses functioned as a check. Bart Ehrman grants the disciples truly believed they had seen Jesus, but explains the appearances as visions. The trouble: hallucinations are private and individual, yet the creed reports group appearances; and the vision theory must still explain the empty tomb and the conversion of skeptics like James and the persecutor Paul — neither driven by grief.

The creed does not by itself prove the resurrection; it proves the belief is early and the witnesses sincere, handing the deeper question to the wider case. But it forecloses the easy theory that the resurrection was a legend grown ripe over generations. That is a great deal for four lines of borrowed Greek to carry.