Full Idea
Frege rejected the traditional categories as importing psychological and linguistic impurities into logic.
Gist of Idea
Frege thought traditional categories had psychological and linguistic impurities
Source
report of Gottlob Frege (Function and Concept [1891]) by Ian Rumfitt - The Boundary Stones of Thought 1.2
Book Reference
Rumfitt,Ian: 'The Boundary Stones of Thought' [OUP 2015], p.18
A Reaction
Resisting such impurities is the main motivation for making logic entirely symbolic, but it doesn't follow that the traditional categories have to be dropped.