P - empirical evidence supporting aspects of the psychodynamic theory.
E - Fisher and Greenberg (1996) summarised 2,500 studies, found support for the existence of unconscious motivation in human behaviour and for defence mechanisms of repression, denial and displacement.
E - despite critics saying no scientific evidence and that it's claims are not testable or falsifiable, many have been tested and confirmed using scientific methodology.
L - strengthens the theory, as it has been looked at objectively and systematically, increasing validity.