To me, there is no such thing as certitude even though I am an atheist. All our science is theory, but because it is far more accurate theory, it is more advanced and enables us to see ourselves and the world about us more realistically. So, science is the main focus of a modern human being, and being scientific means, among other things, that we do not believe or give credit to things or concepts for which there is no evidence. Doing so obstructs the improving of science. We are under no obligation to disprove old theory such as the belief in "spirits." It is as impossible to "prove" "God" does not exist as it is to prove Santa Claus does not exist.
I am not agnostic about "God" anymore than about Santa Claus. Are you?
In the social evolution of mankind, the number of spirits he has worshipped during the last perhaps 100,000 years, the more he needed them to help explain life. As he built up his cultural/technological heritage, the number of spirits he needed to help explain things, declined and his understanding of natural cause and effect increased. The last stages before no "spirits" or atheism was monotheism and deism. Science of the future will depend upon atheism.
That's why my webpage is
http://atheistic-science.com!
charles