Full Idea
It is agreed that all sensible qualities of objects, such as hard or hot, are secondary, and exist in the mind and not in objects; but then this also follows for the primary qualities of extension and solidity.
Gist of Idea
If secondary qualities (e.g. hardness) are in the mind, so are primary qualities like extension
Source
David Hume (Enquiry Conc Human Understanding [1748], XII.I.122)
Book Reference
Hume,David: 'Enquiries Conc. Human Understanding, Morals', ed/tr. Selby-Bigge/Nidditch [OUP 1975], p.154
A Reaction
he mentions Berkeley