Full Idea
It is from the actuality that the potentiality is recognised.
Gist of Idea
We recognise potentiality from actuality
Source
Aristotle (Metaphysics [c.324 BCE], 1051a29)
Book Reference
Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.279
A Reaction
I presume it is from this simple fact that Sider and others draw the mistaken inference that there are no potentialities in the actual world.