W o t D - haeccity

haecceity The essence of a thing.

aspect of existence on which individuality depends

'Thisness'

First proposed by John Duns Scotus (1266-1308), a haecceity is a non-qualitative property responsible for individuation. As understood by Scotus, a haecceity is not a bare particular in the sense of something underlying qualities. It is, rather, a non-qualitative property of a substance or thing: it is a "thisness" (a haecceitas, from the Latin haec, meaning "this") as opposed to a "whatness" (a quidditas, from the Latin quid, meaning "what"). Furthermore, substances, on the sort of metaphysics defended by Scotus, are basically collections of really identical properties ("really identical" in a specialized sense explained below), all but one qualitative; the one non-qualitative property is the haecceity. In contrast to more modern accounts of the problem of individuation, Scotus holds that the haecceity explains more than just the distinction of one substance from another. According to Scotus, the fact that individual substances cannot be instantiated also requires explaining. At issue is something like this: what explains the fact that (e.g) a clone of me is not an instance of me, but an instance of human nature? Haecceities, in addition to explaining distinction, also explain non-instantiability.