Eccéité

Haecceity (hɛkˈsiːɪti,_hiːk-; from the Latin haecceitas, which translates as "thisness") is a term from medieval scholastic philosophy, first coined by followers of Duns Scotus to denote a concept that he seems to have originated: the irreducible determination of a thing that makes it this particular thing. Haecceity is a person's or object's thisness, the individualising difference between the concept "a man" and the concept "Socrates" (i.e., a specific person). In modern philosophy of physics, it is sometimes referred to as primitive thisness. Haecceity is a Latin neologism formed as an abstract noun derived from the demonstrative pronoun "haec(ce)", meaning "this (very)" (feminine singular) or "these (very)" (feminine or neuter plural). It is apparently formed on the model of another (much older) neologism, viz. "qui(d)ditas" ("whatness"), which is a calque of Aristotle's Greek to ti esti (τὸ τί ἐστι) or "the what (it) is." Haecceity may be defined in some dictionaries as simply the "essence" of a thing, or as a simple synonym for quiddity or hypokeimenon. However, in proper philosophical usage these terms have not only distinct but opposite meanings. Whereas haecceity refers to aspects of a thing that make it a particular thing, quiddity refers to the universal qualities of a thing, its "whatness", or the aspects of a thing it may share with other things and by which it may form part of a genus of things. Duns Scotus makes the following distinction: Because there is among beings something indivisible into subjective parts—that is, such that it is formally incompatible for it to be divided into several parts each of which is it—the question is not what it is by which such a division is formally incompatible with it (because it is formally incompatible by incompatibility), but rather what it is by which, as by a proximate and intrinsic foundation, this incompatibility is in it. Therefore, the sense of the questions on this topic [viz. of individuation] is: What is it in [e.g.