Full Idea
Masters and slaves are not masters of slavery or slaves of mastery - they are master or slave of a human being. But mastery is of slavery itself, and slavery of mastery itself. Things don't get powers from forms, nor forms from us.
Gist of Idea
The master-slave relationships are between people, not between mastery and slavery
Source
Plato (Parmenides [c.366 BCE], 133e)
A Reaction
This may be the key objection to platonic forms - that they lack causal powers in the real world. They may therefore fail the only sensible criterion we have for something's existence.
Book Reference
Plato: 'Parmenides', ed/tr. Gill,M.L./Ryan,P. [Hackett 1996], p.136
Related Ideas
Idea 7022 To be is to have a capacity, to act on other things, or to receive actions [Plato]
Idea 8925 Mathematical objects only have properties relating them to other 'elements' of the same structure [Benacerraf]