I believe; and here's one of the reasons why:

I was once visited by two ghosts in my apartment. One was a little boy and the other a little girl. They appeared as very faint ethereal-like images. They were friendly and claimed to be brother and sister. In talking to them, they said they came to stay with me until such time as I met their father. They told me that the only way to connect with him was through someone who truly believes. They told me they wouldn't remain visible all the time, but they wanted me to know they were there, and would be with me until they made their connection with their father. As silly as it sounds, I told them they were welcome to stay with me as long as they needed. For the most part, I forgot about them and generally attributed the apparitions to my over-active imagination. They showed themselves very seldomly, and not for very long, only every now and then, but always in a friendly and excited manner, and while treating the whole experience as though it was happening, I kept telling myself to grow up and just stop believing in these "ghosts" that my mind might be just making up. But I'm a good guy, and I didn't want to intefere with the other side in its attempt to connect with their living family, so I continued to believe. Although to be more honest, I don't think I have ever had any real choice in the matter.
Well, after about a month or two I did meet a guy through a mutual friend. After becoming closer friends, we were both drinking alcohol one night with a few other friends, and he told us all some of his life story. His interest turned solely to me, as everybody else was enjoying the company of others in their drinking and socializing. As I was the only one who stayed interested in his life-story, he told me all kinds of details about crimes he had commited and girlfriends of his. Then he told me about a woman he had a couple of kids with years before and the car accident that killed her (if I recall correctly) and their two young children, a boy and a girl, who were all in the car. He wasn't with them. He was very solemn, and as he continued his story I could not help but feel overwhelmed by the desire to tell him about the ghosts. He told me about how many times he played Russian Roulette with his revolver, if I recall correctly, dozens of times, and other things. As much as I wanted to tell him, I thought he would think I was making fun of his misfortunate life, so I did not ever mention the ghosts of his children to him. Anyways, not many days after (I can't recall exactly as this happened about fifteen years ago) having that conversation with him (mostly just listening though), the two appeared to me again and thanked me for "having them", what I took to mean enduring their stay or something. I told them that I was glad to be of help, and that they were welcome to visit me anytime.

I have grappled with the possibility that my mind made up the ghosts, and that the guy I met, somehow overheard my conversations with those two ghosts via telepathy before I met him, and was relating his story of his children as deception, just to deceive me into believing in ghosts, as a sort of prank. If that were the case, then he could surely not have been the only one to have "overheard". I don't know, and it really doesn't matter anyways, because I have had many encounters with things unexplained, telepathic and otherwise, and I do honestly think, hope, and whatever, that I believe.