per accidens (Latin ‘by accident’), by, as, or being an accident or non-essential feature. A per accidens predication is one in which an accident is predicated of a substance. (The terminology is medieval. Note that the accident and substance themselves, not words standing for them, are the terms of the predication relation.) An ens (entity) per accidens is either an accident or the ‘accidental unity’ of a substance and an accident (Descartes, e.g., insists that a person is not a per accidens union of body and mind.) See also ACCIDENT , ESSENTIALISM , PROPERT. S.J.W.