Full Idea
In his mature nominalism, species and genera are identified with certain mental qualities called concepts or intentions of the mind. Ontologically they are individuals too, like everthing else, ...but they naturally signify many different individuals.
Gist of Idea
Species and genera are individual concepts which naturally signify many individuals
Source
William of Ockham (works [1335]), quoted by Claude Panaccio - William of Ockham p.1056
Book Reference
'Shorter Routledge Encyclopaedia of Philosophy', ed/tr. Craig,Edward [Routledge 2005], p.1056
A Reaction
'Naturally' is the key word, because the concepts are not fictions, but natural responses to encountering individuals in the world. I am an Ockhamist.