On Plurality
Whether all pluralities are extensional is a question that will depend heavily on what a plurality means. The correct way of understanding whether something is a plurality is relative to things of a kind that are more than one in cardinality and are somehow ontologically related to that entity as to be in it in such a way as to make it a plurality. So, for example, a pair of shoes is a plurality just in relation to the shoes that make it a pair. Otherwise, it would just be an object. This relation is sometimes called membership , but this choice of word is confusing because this is also the name of the relationship between sets and their, well, members. Borrowing an idea from Frege, pluralities are always concept-relative. In other words, nothing is a plurality in itself, but most times, the relevant entities that make a plurality a plurality are so contextually salient that we miss this fact. Things get complicate...