Full Idea
To know an effect belongs to a cause, we must also know that that cause belongs to that effect, and this is circular.
Gist of Idea
Knowing an effect results from a cause means knowing that the cause belongs with the effect, which is circular
Source
Sextus Empiricus (Outlines of Pyrrhonism [c.180], III.21)
Book Reference
Sextus Empiricus: 'Outlines of Pyrrhonism', ed/tr. Bury,R.G. [Prometheus 1990], p.193