Full Idea
The Stoics said that the Ideas [Platonic forms] are our own thoughts.
Gist of Idea
Platonic Forms are just our thoughts
Source
report of Stoic school (fragments/reports [c.200 BCE]) by Pseudo-Plutarch - On the Doctrine of the Philosophers 882a
A Reaction
That's Plato deftly kicked into touch. I'm with the Stoics.
Book Reference
'The Stoics Reader', ed/tr. Inwood,B/Gerson,L.P. [Hackett 2008], p.86