I asked bruce to tell his experience, and then told two of my own. while mine don't have anything to do with UFOs, they are experiences that cannot be proven in any way, although they were witnessed. Just as bruce's experience was witnessed and also experienced by another person present.

witness ..
witness :
       n 1: someone who sees an event and reports what happened [syn: witnesser,
             informant]
       2: a close observer; someone who looks at something (such as an
          exhibition of some kind); "the spectators applauded the
          performance"; "television viewers"; "sky watchers
          discovered a new star" [syn: spectator, viewer, watcher,
          looker]
       3: testimony by word or deed to your religious faith
       4: (law) a person who attests to the genuineness of a document
          or signature by adding their own signature [syn: attestant,
          attestor, attestator]
       5: (law) a person who testifies under oath in a court of law
       v 1: be a witness to