What is "haecceity"

Haecceity \H[ae]c*ce"i*ty\ (h[e^]k*s[=e]"[i^]*t[y^]), [L. h[ae]cce this.] (Logic) Literally, this-ness. A scholastic term to express individuality or singleness; as, this book.

n. The essence of a particular thing; those quality that define it and make it unique.

n. the essence that makes something the kind of thing it is and makes it different from any other [syn: quiddity]

Haecceity (; 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. It denotes the discrete qualities, properties or characteristics of a thing that make it a particular thing. Haecceity is a person or object's thisness, the individualising difference between the concept 'a man' and the concept 'Socrates' (a specific person). Haecceity is a literal translation of the equivalent term in Aristotle's Greek to ti esti (τὸ τί ἐστι) or "the what (it) is."

Charles Sanders Peirce later used the term as a non-descriptive reference to an individual.