Abstract
This article examines the epistemological methods of rationalism, empiricism, and intuitionism with regard to their use during three periods of history: 1) until the sixteenth century, 2) from the seventeenth to the twentieth century, and 3) the second half of the twentieth century. It emphasizes the importance of clarifying underlying epistemological differences among 1) psychological theories and methods, 2) worldviews influencing patients, and 3) assumptions of which psychotherapists are not aware but which they bring to therapy sessions.