Well, perhaps having the feeling
that there are ghosts, even in the absence of thinking you see something, is a kind of evidence.
I'm of two minds about the whole thing. Part of me is a hardnosed skeptic, but I have a couple of friends and family members that have had odd things happen, and I've had the occasional odd thing myself. So the other part of me doesn't think either option is nutty.
In general, however, I think basing belief on one's own observations of anything is the better strategy, so seeing would be slightly less nutty.