It has often been said that no one knows what psychoanalysis is—whether it is a science, one of the humanities, a particular type of therapeutic art, a religion or a form of semantic theory (Ryecroft 1968). There are those who postpone judgement, waiting to see whether psychoanalytical theory is refuted or accepted. This raises the question of the nature of theories developed to explain human nature, as opposed to those designed for the purpose of explaining physical nature. Failure to distinguish between them leads to much confusion. Consideration of human nature leads to what is exclusively and most significantly human—human experience, so-called psychic reality, a phenomenon unique to human beings, but shared to a certain extent by them, and capable of communication between them. Physical nature, both organic and inorganic, is of a different order of abstraction. Psychic reality, which cannot be directly perceived through the physical senses, is only directly experienced in the self, but can be communicated by language—and can be inferred from observation. Physical reality can only be perceived through the physical senses.