Full Idea
In reality [eteé] to recognise what sort each thing is, belongs to what is impracticable [aporos].
Gist of Idea
It is not possible to know what sort each thing is
Source
Democritus (fragments/reports [c.431 BCE], B008), quoted by Sextus Empiricus - Against the Logicians (two books) 7.137
Book Reference
Democritus: 'Early Greek Phil VII: Democritus', ed/tr. Laks,A/Most,G [Harvard Loeb 2016], p.79
A Reaction
On the whole modern scientists (and the rest of us) shoehorn virtually everything into a specific category. It strikes me as wildly bad metaphysics to say that everything necessarily has its category.