In
Carlos Castaneda's books, his teacher
Don Juan talks much about becoming and being a "man of knowledge," without giving a concise definition.
Translating into the language of other spiritual paths, a man of knowledge could be loosely described as a person who has acheived enlightenment, or a person who understands deeply themselves and the most intrinsic aspects of the world they live in.
To Don Juan, becoming a man of knowledge involves the use of hallicinoigens. It is a dangerous path, but for him and for Castaneda, it is a path with a heart.