An idea.
The conceptuals used to say that the idea was the work.
In his manifesto, Stephen Willats brings in other determining factors: behaviors, and cognition.
So the conceptual model doesn't stop at the idea: embodied in behaviors, ideas work their ways through the circuits of cognition.
Why is this important?
Because it allows to underline the epistemological scope of art, suggesting that its action modifies the genealogical relations to knowledge.