The distinction between "primary and secondary qualities," first stated and thus named by Robert Boyle, received its classical formulation in John Locke's Essay. There Locke states that apart from ordinary causal properties or "powers," material objects possess five primary qualities—extension (size), figure (shape), motion or rest, number, and solidity (impenetrability)—and many secondary qualities, such as color, taste, smell, sound, and warmth or cold. This distinction was made in the context of representative realism; that is, it was presupposed that the qualities of objects are quite distinct from, and are in fact causes of, "ideas" (representations or sensa), which are the only immediate objects of sensory awareness. The basis of the distinction was twofold. First, perceived size, shape, motion, number, and solidity are ideas caused by and exactly resembling the corresponding primary qualities of objects; perceived color, taste, smell, sound, and...