haecceitas

“Scotus called haecceitas, that irreducible this-ness that God had in mind in creating an individual.”

The Corner on National Review Online

“This, in its turn, is followed by a nod to Gerard Manley Hopkins's use of the word "haecceitas," referring to an entity's individual "thisness," which, Vendler reminds us, he borrowed from the medieval philosopher Duns Scotus.”

The Washington Post: Helen Vendler's new commentary on Emily Dickinson, reviewed by Michael Dirda

“If there were, then there would have to be a haecceitas or thisness belonging to and individuating each complex physical object, and this I am assuming to be implausible if not unintelligible.”

Dualism

“(More about the conditions under which haecceitas can make sense will be found below.)”

Dualism

“(haecceitas) is the immanent principle of individuation, whereas form, matter, and quantity are the remote principle.”

Paul of Venice

“Of the propositions which have been accepted or at least favourably treated by a large number of scholars, we may mention: the Scotist view of the relation between essentia and existentia; that between ens and nihil the distance is not infinite but only as great as the reality that the particular ens possesses; that the accidens as such also possesses a separate existence (e.g. the accidentia of bread and wine in the Eucharist); that not only God, but also man can produce an esse simpliciter (e.g. man by generation); haecceitas as the principium individuationis.”

The Catholic Encyclopedia, Volume 13: Revelation-Stock