The philosopher Karl Popper, who argued that all proper scientific theories must be potentially falsifiable, claimed that Freud's Psychoanalytic Theories were presented in unfalsifiable form, meaning that no experiment could ever disprove them. The philosopher Adolf Grünbaum argues in "The Foundations of Psychoanalysis" (1984) that Popper was mistaken and that many of Freud's theories are empirically testable, a position with which others such as Eysenck agree. The philosopher Roger Scruton, writing in "Sexual Desire" (1986), also rejected Popper's arguments, pointing to the theory of repression as an example of a Freudian theory that does have testable consequences. Scruton nevertheless concluded that psychoanalysis is not genuinely scientific, on the grounds that it involves an unacceptable dependence on metaphor. The philosopher Donald Levy agrees with Grünbaum that Freud's theories are falsifiable but disputes Grünbaum's contention that therapeutic success is only the empirical basis on which they stand or fall, arguing that a much wider range of empirical evidence can be adduced if clinical case material is taken into consideration.