Definitions

Primary and Secondary Qualities

John Locke (1632 - 1704) used [the] notion of primary and secondary qualities. Primary qualities are qualities which an object actually has, regardless of the conditions under which it is being perceived, or of whether it is being perceived at all. Primary qualities include size, shape and movement….

….Secondary qualities include colour, smell, and taste. It may seem as if these are really in the objects we perceive, so that redness is somehow part of a red dress. But, in fact, what redness is is a power to produce red images in a normal viewer under normal conditions. Redness isn't part of a red dress in the way that its shape is. Ideas of secondary qualities don't resemble the actual objects, but, rather, are in part a product of the kind of sensory system we happen to have.

Philosophy: The Basics. Nigel Warburton. Third edition. Page 102. (Routledge 1999).