Authors:

We can study various psychic functions and also the more primitive sensory functions, such as seeing, hearing, and so on, which constitute our image of our everyday world. They have a material side and the psychic side. And that is a gap which you cannot explain.

"Stanislav Grof interviews Dr. Albert Hofmann Esalen Institute, Big Sur, California". Interview with Stanislav Grof, www.maps.org. 1984.
We can study various psychic functions and also the more primitive sensory functions, such as seeing, hearing, and so on, which constitute our image of our everyday world. They have a material side and the psychic side.