Full Idea
Those who can see each thing in itself, in its permanent and unvarying nature, we'll say they have knowledge and are not merely entertaining beliefs.
Gist of Idea
Knowledge must be of the permanent unchanging nature of things
Source
Plato (The Republic [c.371 BCE], 479e)
Book Reference
Plato: 'Republic', ed/tr. Waterfield,Robin [OUP 1993], p.202