Full Idea
The root problem of the theory of Forms is that they posit Forms that are universal and at the same time Forms that are separable and therefore particular.
Gist of Idea
There is a confusion because Forms are said to be universal, but also some Forms are separable and particular
Source
Aristotle (Metaphysics [c.324 BCE], 1086a28)
Book Reference
Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.424