Full Idea
There is doubt about whether our experience of the world is such that we can conceive of the sort of separation of primary and secondary qualities which the scientific view calls for, and can understand what the world is like with no secondary qualities.
Gist of Idea
We can't grasp the separation of quality types, or what a primary-quality world would be like
Source
Jonathan Dancy (Intro to Contemporary Epistemology [1985], 10.3)
Book Reference
Dancy,Jonathan: 'Introduction to Contemporary Epistemology' [Blackwell 1985], p.149
A Reaction
Dancy attributes these doubts to Berkeley (e.g. Idea 3837). I think what is claimed here is false. Obviously we spend our whole lives immersed in secondary qualities, but separating the different aspects is precisely what scientists (and philosophers) do.
Related Idea
Idea 3837 We can't understand something as a lie if beliefs aren't commitment to truth [Searle]