Entry 0380: Aristotle accipit esse pro quidditate
When addressing the issue of what
Aquinas meant by the term “ens,” Jan
A. Aertsen remarks that it is through the notion of “actuality” that Aquinas’s
conception of ens is best understood.
According to Aertsen, Aquinas explicitly distinguishes himself from Aristotle
precisely on this, that for Aquinas esse
means actus entis whereas for
Aristotle esse means quiddity. Thus
Aertsen writes:
See J. A. Aertsen, Medieval Philosophy and the
Transcendentals: The Case of Thomas Aquinas (Leiden
“The distinctive feature of
Thomas’s understanding of being is the notion of ‘actuality.’ In his own
judgment he differs in this respect from Aristotle, who conceived ‘being’ as
the quiddity of something:
“‘Philosophus non accepit esse secundum quod dicitur actus entis (…), sed accipit esse pro quidditate, vel ratione, quam significat definitio’
(Aquinas, In III Sententiarum,
distinction 8, question 1, article 5, ad 2).”