What makes you unbelieve Crash ?

This reminds me of a conversation I had with my significant other. She is Catholic and has lived in a family which believe in witches and ghosts and other supernatural things. An ongoing discussion we have is on whether ghosts exist. She asked me what kind of evidence ity would take for me to believe in ghosts. I told her that even if I thought I saw a ghost myself I wouldn't believe it because I understand that the brain can see things which aren't there, especially at night. I told her that if we both saw the "ghost"; then wrote down independantly and privately, without consulting each other, a description of what we saw and both descriptions matched, then I may lean towards believing. I would still need more evidence to be secure in that idea, but I would give the idea of ghosts a more serious glance and lean towards believeing they probably exist. I especially like the saying by Carl Sagan who said something like -Extraordinary claim's require extraordinary evidence.