Full Idea
Is it a necessary condition on possessing the concepts of 'two' and 'green' that one does not believe that two is green? I think this claim is false.
Gist of Idea
To grasp 'two' and 'green', must you know that two is not green?
Source
Ofra Magidor (Category Mistakes [2013], 3.4)
Book Reference
Magidor,Ofra: 'Category Mistakes' [OUP 2013], p.61
A Reaction
To see that it is false one only has to consider much more sophisticated concepts, which are grasped without knowing their full implications. I might think two is green because I fully grasp 'two', but have not yet mastered 'green'.