Every “good” scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is.
conjectures And Refutations: The Growth Of Scientific Knowledgeby karl Popper
Every genuine test of a theory is an attempt to falsify it, or to refute it. Testability is falsifiability; but there are degrees of testability: some theories are more testable, more exposed to refutation, than others; they take, as it were, greater risks.
