Full Idea
Some thinkers (e.g. Locke) understand by matter an inert, senseless substance, in which extension, figure and motion do actually subsist.
Gist of Idea
Locke believes matter is an inert, senseless substance, with extension, figure and motion
Source
report of John Locke (Essay Conc Human Understanding (2nd Ed) [1694]) by George Berkeley - The Principles of Human Knowledge §9
Book Reference
Berkeley,George: 'The Principles of Human Knowledge etc.', ed/tr. Warnock,G.J. [Fontana 1962], p.69
A Reaction
Berkeley, of course, goes on to reject this. Personally I agree with Locke, because I am a realist, and I think the seventeenth century distinction between primary and secondary qualities is a key contribution to human understanding.