Those who seek this knowledge are of three kinds.

1. First there is the student who studies it from authentic sources, in order to discover some theory that his reason can accept intellectually.
2. Then there is the adept. His way is the way of meditation; by meditation he develops that state in which he is as though dead, in which he can rise above the life of the material body, even if only for a moment; and in that way he experiences life after death, which is the beginning of the knowledge of immortality.
3. And thirdly there is the person who wishes to communicate with spirits so as to know about their condition. If he is himself capable of communicating with spirits he can, to a certain extent, get the knowledge from them.