" Piaget is also concerned with attempts of Maine de Biran, Bergson, Sartre, and Merleau-Ponty to construct a philosophical psychology as opposed to a scientific empirical psychology. He believes that the difference between philosophical psychology and scientific psychology lies neither in the fact that the former concerns itself with “essences” (Husserl), with “irrationality” (Sartre), nor in its use of introspection. He sees the difference as being one rather of method: philosophical psychology neglects objective verification and grounds itself in subjectivity, although claiming to arrive at objective knowledge through intuition. "

― Jean Piaget , Insights and Illusions of Philosophy: Selected Works Vol 9