Dodo bird verdict
Some people say that all empirically validated psychotherapies have similar outcomes, no matter what their components are. This is known as Dodo bird verdict, or Dodo bird conjecture in psychotherapy. Saul Rosenzweig introduced the concept in 1936, and named it after Dodo, a character from Lewis Caroll's book Alice in Wonderland.  The topic is controversial. It only became widely known with new research evidence, in the 1970s.