Haecceity

Haecceity (/hɛkˈsɪti, hk-/; from the Latin haecceitas, '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 person" and the concept "Socrates" (i.e., a specific person). In modern philosophy of physics, it is sometimes referred to as primitive thisness.