Primary quality

In John Locke's account, a quality such as extension, solidity, shape, number or motion, attributed to bodies independently of whether they are perceived. This historical list should not be treated as an unrevisable inventory of fundamental physical properties.

In John Locke's terminology, a body's exclusion of another body from the space it occupies. This is not the material-science notion of hardness: John Locke treats water as solid in this sense while distinguishing its yielding response from a diamond's resistance.^[ref]