Full Idea
The One has no share of time, nor is it in any time. …The One in no way partakes of being, so the One in no way is. …The One neither is one nor is. …It is not named or spoken of, nor is it the object of opinion, nor does anything that is perceive it.
Gist of Idea
The One is timeless, has no being or identity, and cannot be known
Source
Plato (Parmenides [c.366 BCE], 141d-142a)
Book Reference
Plato: 'Complete Works', ed/tr. Cooper,John M. [Hackett 1997], p.375
A Reaction
[Phrases lifted from a page-long detailed argument] Given all of this, it is surprising that the One is not dismissed entirely. That leaves it as an object of mystical belief.