The importance and difficulty of validating psychoanalytic interpretations at the time they are made led the author to propose an existential hypothesis method, which involves formulating fundamental psychoanalytic theories as existential hypotheses (i.e., hypotheses that claim the theories are true at least for one case but not necessarily for all) and using a form of deductive reasoning (disjunctive syllogism) to validate interpretations. The method is illustrated by applying it to two interpretations, one of which is rejected and the other accepted. Some questions and criticisms are addressed.