Your friend saw this resource on bethinking.org and thought you should see it:
Was the Resurrection a Hallucination?
Is it possible that the accounts of the resurrection are simply the result of hallucinations brought on by grief?
See the full resource online by visiting bethinking.org:
https://www.bethinking.org/did-jesus-rise-from-the-dead/resurrection-hallucination
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bethinking.org is a collection of resources which aims to make sense of the big questions of life about God, Jesus and Christianity.