Full Idea
As we approach to or recede from an object, the visible extension varies, being at one distance ten or a hundred times greater than at another; doth it not follow that it is not really inherent in the object?
Clarification
'Visible extension' is the apparent size. 'Small cows distant, big cows close'.
Gist of Idea
The apparent size of an object varies with its distance away, so that can't be a property of the object
Source
George Berkeley (Three Dialogues of Hylas and Philonous [1713], I p.171)
Book Reference
Berkeley,George: 'The Principles of Human Knowledge etc.', ed/tr. Warnock,G.J. [Fontana 1962], p.171
A Reaction
Berkeley is confused, because he is too literally empirical. Qualities are not self-evidently primary or secondary, but are judged so after comparisons (e.g. with testimony, or with the other senses).