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.

Lakatos (1978, p. 31) cited in: Jean Pierre Colson (1989) Krashens Monitortheorie. p. 40.