Karl Popper (1902-94) set up a criterion: THEORIES can be divided into those that are SCIENTIFIC (i.e. disprovable) and those that are NON-SCIENTIFIC (i.e. not disprovable). NON-SCIENTIFIC THEORIES include: most religious ideas (e.g. The Existence of God), many political ideas (Marxism, Capitalism), Freudian ideas (e.g. the contents of the Unconscious Mind), and daily horoscopes found in newspapers.
