The distinction between primary and secondary qualities is an important issue in metaphysics, particularly in discussions concerning the nature of objects, perception, and the relation between mind and reality. The distinction was developed prominently by philosophers such as Galileo, Descartes, John Locke, and later discussed critically by Berkeley. It attempts to explain which properties belong objectively to material objects and which arise through the interaction between objects and perceiving subjects. Primary qualities are properties considered to exist in objects independently of whether anyone perceives them. They are regarded as objective features of material bodies. John Locke identified several primary qualities, including solidity, extension, figure, motion or rest, and number. For example, a table has a particular size, shape, and spatial extension whether or not anyone is looking at it. Similarly, the number of objects in a room does not depend upon a person's perception of them. Primary qualities are therefore thought to be