A man confidently and in vivid detail describes attending a family event that, according to every other family member present and all available records, simply never took place. He is not lying — he genuinely believes it happened and experiences the memory with full conviction. What is this?

This is a false memory: a confidently held memory of an event with no basis in fact, where the person is not lying and experiences the memory with the same subjective conviction as a genuine one. It is not a screen memory, since a screen memory requires that a real event genuinely underlies it, with only part of it substituted, whereas here no such underlying event exists at all according to every other source. It is not retrospective falsification, in which a real event is recalled but coloured by mood — again, no real event underlies this account. And it is not confabulation, which typically arises alongside an organic memory gap that needs filling, rather than a standalone, fully-formed false recollection of this kind.