For the sophisticated falsificationist a scientific theory T is falsified if and only if another theory T' has been proposed with the following characteristics :
(1) T' has excess empirical content over T: that is, it predicts novel facts, that is, facts improbable in the light of, or even forbidden, by T;
(2) T' explains the previous success of T, that is, all the unrefuted content of T is included (within the limits of observable error) in the content of T'; and
(3) some of the excess content of T' is corroborated.