According to Hans Holzer, a psychical researcher, he differentiates between ghosts and spirits. Ghosts, he says, are continuous replays of events, such as the ghosts that people see at places like Gettysburg, where they can see reenactments of battles. The ghosts aren't aware of the presence of humans because they have no real "life" of their own; it's merely a replay, such as watching a movie over and over again. We can observe them but we can't interact in any way. Spirits, however, according to Holzer, are souls who have pierced the veil, crossed over to the other side and can and do make contact w/those of us still here on earth. As someone who has been involved w/the spirit realm my entire life, I subscribe to this belief as well. So. Can cats see ghosts? Yes. Can they see spirits? Yes. Animals, children, the elderly and those who are ready to make their transition can see and communicate w/them because they are more sensitive as they are closest to the the thinning veil between the worlds. As we enter into the dark of the year, people and animals will have more experiences w/spirits, Samhain (Halloween) being the night when the veil between the worlds is at its thinnest. My black Halloween cat, Boo, sometimes stares at something and watches intently and I know that he's making contact. All of my cats do it but especially Boo.