Full Idea
The problem endlessly debated is how, from such a unity as we have declared the One to be, does anything at all come into substantial existence, any multiplicity, dyad or number?
Gist of Idea
How can multiple existence arise from the unified One?
Source
Plotinus (The Enneads [c.245], 5.1.06)
Book Reference
Plotinus: 'The Enneads', ed/tr. Mackenna,Stephen [Penguin 1991], p.353
A Reaction
This was precisely Aristotle's objection to the One of Parmenides, and especially the problem of the source of movement (which Plotinus also notices).