Full Idea
The one was and is and will be and was becoming and is becoming and will become.
Gist of Idea
The one was and is and will be and was becoming and is becoming and will become
Source
Plato (Parmenides [c.366 BCE], 155d)
Book Reference
Plato: 'Plato IV (Cratylus,Parmenides,Hippias Maj, Min)', ed/tr. Fowler,H.N. [Harvard Loeb 1926], p.295
A Reaction
This seems to be rhetorical, rather a precise theory, given that the One is said to be eternal and unchanging. The One is not just what we call 'reality'.
Related Idea
Idea 453 Reality is symmetrical and balanced, like a sphere, with no reason to be greater one way rather than another [Parmenides]