Popular rules of inference in propositional logic include "modus ponens", "modus tollens", and contraposition. A proof by contraposition (contrapositive) is a direct proof of the contrapositive of a statement. See also contraposition and proof by contrapositive. Therefore, by contraposition, a necessary condition for unit-treatment additivity is that the variance is constant. Hence, the subjective Bayes' theorem represents a generalization of both "contraposition" and Bayes' theorem . In some cases, contraposition involves a change of the former's quality (i.e. affirmation or negation). Hence, Bayes' theorem represents a generalization of "contraposition" . Strictly speaking, a contraposition can only exist in two simple conditionals. He is unsatisfied with the oversimplified polar contraposition between patriotism and rusophobia. Note that the method of transposition and contraposition should not be confused. The contraposition with De Gasperi was very clear. However, a contraposition may also exist in two complex, universal conditionals, if they are similar. The album focuses on the contraposition of "love" and "not-love". Transposition is exactly the same thing as Contraposition, described in a different language. Although a direct proof can be given, we choose to prove this statement by contraposition.