It would be nonsense to say we regard something as sure evidence because it is certainly true. Rather, we must first determine the role of deciding for or against a proposition…. The proposition is either “true or false” only means that it must be possible to decide for or against it. But this does not say what the ground for such a decision is like.

There is a vast and controversial literature concerning the efficacy of psychoanalysis, both within and outside the field.