Ousia - Philosophical and Scientific Use

Philosophical and Scientific Use

Aristotle defined protai ousiai, or “primary substances”, in the Categories as that which is neither said of nor in any subject, e.g., “this human” in particular, or “this ox”. The genera in biology and other natural kinds are substances in a secondary sense, as universals, formally defined by the essential qualities of the primary substances; i.e., the individual members of those kinds.

Much later, Martin Heidegger said that the original meaning of the word ousia was lost in its translation to the Latin, and, subsequently, in its translation to modern languages. For him, ousia means Being, not substance, that is, not some thing or some being that "stood"(-stance) "under"(sub-). Moreover, he also uses the bi-nomial parousia-apousia, denoting presence-absence, and hypostasis denoting existence.