  We should note that in the context of Porphyry’s discussion, we are dealing with indefinite descriptions, given that the stipulation that Sophroniscus has only one son is not part of the phrase but merely background information.  This fact is enough to ensure that the phrase in fact refers to only one individual, but it does not alter the linguistic generality of the phrase.  There was little specific discussion of definite descriptions, but it seems that they would have been treated in the same way. John Buridan has the most direct discussion of the issue. In one place he considers the phrase, ‘first Christian king of France’ (primus rex Francie christianus).  This he took to be general, insofar as it is made up of common concepts.  In another place he considers the phrase ‘largest and brightest heavenly body’ (planeta maximus et lucidissimus) used to refer to the sun, and he remarks that the very same phrase, without any new imposition, could supposit for a second sun if God were to create another, either similar or greater in size and brightness.  He could be interpreted as saying that the very same phrase, without being given any new signification, could refer to different individuals in different possible worlds.