Full Idea
In general one can find nothing in our conceptions that is not known to oneself in direct experience. For it is grasped either by similarity to what is revealed in direct experience, or by expansion or reduction or compounding.
Gist of Idea
All our concepts come from experience, directly, or by expansion, reduction or compounding
Source
report of Stoic school (fragments/reports [c.200 BCE]) by Sextus Empiricus - Against the Mathematicians 8.58
A Reaction
Although the stoics allow for purely a priori knowledge, this quotation sounds comprehensively empirical.
Book Reference
'The Stoics Reader', ed/tr. Inwood,B/Gerson,L.P. [Hackett 2008], p.50
Related Idea
Idea 20785 Our conceptions arise from experience, similarity, analogy, transposition, composition and opposition [Stoic school, by Diog. Laertius]