Scholastic logicians also drew a sharp distinction between logic and
ontology, taking the latter to be about ‘first intentions’ (concepts abstracted directly from physical reality), and the former about ‘second intentions’
(concepts abstracted wholly from the ‘material’ content of first inten-
tions, as well as about such categorial concepts as individual, proposition,
universal, genus, species, property, etc., and so-called syncategorematic
concepts such as negation).
According to Aquinas, second intentions have
a foundation in real entities, but ‘exist’ only in knowledge; i.e., they do not
exist in the real world but depend on the mind for their existence – which
is not say that they are subjective mental entities.