Hecceity

An object, in so far as it is denoted by an index, having thisness, and distinguishing itself from other things by its continuous identity and forcefulness, but not by any distinguishing characters, may be called a hecceity. A hecceity in its relation to the assertion is a subject thereof.

By a hecceity, I mean, some element of existence which, not merely by the likeness between its different apparitions, but by an inward force of identity, manifesting itself in the continuity of its apparition throughout time and in space, is distinct from everything else, and is thus fit (as it can in no other way be) to receive a proper name or to be indicated as this or that.