 In 1974, David Miller and Pavel Tichý, working independently, demonstrated that the conditions specified by Popper in his accounts of both qualitative and quantitative verisimilitude for comparing the truth- and falsity-contents of theories can be satisfied only when the theories are true. In the crucially important case of false theories, Popper’s definitions are formally defective: for with regard to a false theory \(t_2\) which has excess content over a rival theory \(t_1\), both the truth-content and the falsity-content of \(t_2\) will exceed that of \(t_1\). With respect to theories which are false then, Popper’s conditions for comparing levels of verisimilitude, whether in quantitative and qualitative terms, can never be met.