  The second way in which Buridan changed the dialectical landscape was to extend the range of traditional logic. There are numerous examples of this, not all of which are uncontroversial because it is often hard to tell what Buridan intended to achieve by a given innovation (this goes for other medieval logicians as  well).[21]  But a fairly uncontroversial example can be found in his use of supposition to examine the structure of certain complex terms that would remain unanalyzed on the traditional account of syllogistic inferences. Of particular importance here is the doctrine of ampliation. Thus, although the syllogism, ‘Nothing dead is an animal, some man is dead; therefore, some man is not an animal’, is an acceptable fourth-mode syllogism of the first figure (Ferio), Buridan denies that the consequence is “formally valid”. The reason is that in this syllogism, ‘man’ is an ampliative term, and “from an ampliated nondistributed term the same term does not follow nonampliated” that is, “in the minor proposition the term ‘man’ was ampliated to past [things], whereas in the conclusion it was not ampliated,” making the premises true but the conclusion false (S 5.3.2: 326; cf. QAnPr I.14). Similarly, terms referring to the divine persons sometimes generate counterexamples to the traditionally accepted modes. Thus, “the following syllogism in Barbara is invalid: ‘Every God is the son, every divine Father is God; therefore every divine Father is the Son”, for the transitivity of identity fails in cases “where the most simple unity is a trinity of really distinct persons” (S 5.3.2: 327). Buridan also urges the reader to be wary of modal contexts introduced by verbs of knowing and believing because “the verb ‘know’ ampliates the subject to supposit not only for present things, but also for future and past ones”. This means that without suitable qualification, “although I know that every man is an animal, nevertheless, it does not follow that every man is known by me to be an animal; for then it would follow that every man, whether alive or dead or yet to be born, would be known by me to be an animal, which is false” (S 5.6.8: 348). What is noteworthy in these and other examples is Buridan's use of the doctrine of supposition to extend the range of ‘truth-makers’ for modal inferences, e.g., in his assumption that “the presence of a modal copula—any modal copula—in a proposition ampliates the subject to stand for not only the actual things but also the possible things that fall under that  term”.[22]  Because it makes merely possible objects relevant to the evaluation of modal inferences, ampliation can be seen as a kind of Buridanian equivalent of possible worlds semantics, though it would be a mistake to regard it as a remarkable anticipation of that twentieth-century doctrine. Buridan's remarks on its theoretical significance are  few,[23]  and, despite the degree of technical sophistication involved, he probably did not see it as a radical innovation, but as part of his ongoing effort to make existing schemes for checking inferences more practicable.