Greek ἐνάργεια (enargeia); Latin evidentia (Cicero)
The vividness or self-evidence of what is directly perceived. For Epicurus, clear evidence is the foundation of all knowledge: we reason from what is evident to what is not, and nothing that is evident can be overturned by argument.
1. Key Texts
Quote from Epicurus, Letter to Herodotus 82So we should pay heed to those feelings which are present in us, and to our sensations - universal sensations for universal matters, particular ones for particular matters - and to all self-evidence which is present by virtue of each of the discriminatory faculties. (tr. Long & Sedley)