Karl Popper wrote "A theory is part of empirical science if and only if it conflicts with possible experiences13 and is therefore in principle falsifiable by experience." The idea here is that if you can't prove something wrong, you can't really prove it right either.

Thus, in Popper's words, science requires testability: "If observation shows that the predicted effect is definitely absent, then the theory is simply refuted." This means a good theory must have an element of risk to it—namely, it has to risk being wrong. It must be able to be proven wrong under stated conditions.