They may be good in their specialized field, but they have blinders on concerning the complexity and realm of possibilities in this Universe. Certainly there are many things in the world and in life they we do not know about nor do we understand. Enough people believe that there is some spiritual essence that there must be something to it. At the very least, it is possible that there are spirits. We will probably never know for sure one way or the other.
Some people claim to have seen and even heard spirits.
It is so difficult to verify this, since it could easily be imagined or even made up. The ghost of Babe Ruth Years ago I had a poster of the famous baseball player Babe Ruth on the wall in my bedroom. One night I woke up in the middle of the night and saw a white figure of the Babe at the foot of my bed. I got so scared that I threw my pillow at the apparition to chase it away. This happened several times, so I finally took down the poster.