Full Idea
The Soul maintains its unfailing movement; for not all that passes in the soul is, by that fact, perceptible; we know just as much as impinges on the faculty of the sense.
Gist of Idea
The movement of Soul is continuous, but we are only aware of the parts of it that are sensed
Source
Plotinus (The Enneads [c.245], 5.1.12)
Book Reference
Plotinus: 'The Enneads', ed/tr. Mackenna,Stephen [Penguin 1991], p.360
A Reaction
This is a straightforward argument in favour of an unconscious aspect to the mind - and a rather good argument too. No one thinks that our minds ever stop working, even in sleep.