Part of Berkeley's strategy in his attack on materialism in the Three Dialogues Between Hylas and Philonous is to argue that the epistemological distinction between ideas of so-called primary qualities and ideas of secondary qualities, especially as this distinction is found in Locke, is untenable. Both kinds of ideas-those presenting to the mind the quantifiable properties of bodies and those which are just sensations -are equally perceptions in the mind, and there is no reason to believe that one kind represents (...) true properties of independently existing external objects while the other kind does not. (shrink)