Full Idea
We might say that scepticism is ruled out for secondary qualities because (roughly) phenomenalism is correct for them; but phenomenalism is not similarly correct for primary qualities, and scepticism cannot get a foothold.
Gist of Idea
Phenomenalism is correct for secondary qualities, so scepticism is there impossible
Source
Colin McGinn (Subjective View: sec qualities and indexicals [1983], 2)
Book Reference
McGinn,Colin: 'The Subjective View' [OUP 1983], p.12
A Reaction
An odd idea, if phenomenalism says that reality consists entirely of phenomena. I should think phenomenalism is a commitment to the absence of primary qualities.
Related Idea
Idea 7301 The phenomenalist says that to be is to be perceivable [Cardinal/Hayward/Jones]