 Just as the past tense ampliates the subject to include past as well as present supposita, modal verbs ampliate the subject to possible supposita, as do verbs such as ‘understand’, ‘believe’, and indeed, notes Albert of Saxony, verbal nouns ending in ‘-bile’: ‘possible’, ‘audible’, ‘credible’, ‘capable of laughter’ and so on. Albert realises that even ‘supposit’ ampliates the subject: when we say ‘This term supposits for something’, what it supposits for need not actually exist, but might be past, future, possible or merely intelligible. According to Buridan, ‘must’ ampliates for possible supposita, for ‘A must be B’ means ‘It is not possible that A not be B’, contradictories must clearly ampliate in the same way, and ‘It is possible that A not be B’ ampliates for possibilia. Ampliation over possibles means care is needed in inferences from ‘is’ to ‘can’: ‘A can be B’ need not follow from ‘A is B’, for ‘A can be B’ means that what is or can be A can be B, and even if A is B, not everything which can be A might be capable of being B. For example, ‘Every planet lighting our hemisphere can be the sun’ is false even though it is in fact the sun which lights it, since the moon might light our hemisphere but the moon cannot be the  sun.[30]