Psychological theories must be all-inclusive (anamnestic), coherent, consistent, logically compatible, insightful (diagnostic), aesthetic, parsimonious, explanatory, predictive (prognostic), therapeutic, imposing, and elastic.
But psychology is constrained because its experiments have to be ethical and are subject to the Psychological Uncertainty Principle: they are unique and lead to under generation of testable hypotheses. The psychological theories underlying psychotherapy, though, are good as organizing principles, integrative principles, and purgatory principles.
