QUALITIES. Primary qualities of matter are, mainly, the spatio-temporal ones, such as shape or motion; secondary ones are the sensible qualities, such as colour or smell. "Tertiary qualities" is a new and convenient term, introduced by Bosanquet, among others, to designate what are commonly called the ultimate values, beauty, goodness, truth.
Primary and Secondary Qualities.—The distinction be tween primary and secondary qualities is given officially for British philosophy by Locke (Essay, Bk. ii., ch. viii. secs. 9, o). "Qualities thus considered in bodies are First, such as are utterly inseparable from the body in what estate soever it be; such as, in all the alterations and changes it suffers, all the force can be used on it, it constantly keeps; and such as sense constantly finds in every particle of matter which has bulk enough to be perceived, and the mind finds inseparable from every particle of matter, though less than to make itself singly be perceived by our senses." Locke enumerates: "solidity, extension, figure, motion or rest and number." Secondly, "Such qualities, which in truth are nothing in the objects themselves, but powers to produce various sensations in us by their primary qualities, i.e., the bulk, figure, texture and motion of their insensible parts, as colours, sounds, tastes, etc., these I call secondary qualities." Locke adds that there is a third set of qualities, which are powers to produce changes in other bodies, not merely sensations in us. The dis tinction of primary and secondary qualities does not originate with Locke. It occurs in Greek philosophy in the doctrine of Democritus: "Sweet and bitter exist by law or convention" (that is, are relative to us) ; "what exists in reality are the atoms and the void." The atoms, which possess shape and other "primary" qualities, themselves by their density account for such qualities as heavy or hard; but other qualities are the effect upon us of the atoms. Aristotle makes the distinction on a quite different basis, and probably the more valuable one. He distinguishes (De Anima, ii., 5) the special sensibles, like colour or taste, which are apprehended by only one sense, from the common sensibles, ap prehended by all the senses alike, motion, rest, etc. For modern
philosophy, the distinction of primary qualities from secondary ones, in much the same form as Locke's, begins with Galileo, who goes so far even as to say that secondary qualities are but names which we give to things because they excite certain sensations in us (Hoeffding, Hist. Phil., vol. i., p. 183). Locke derived his statement of the distinction from Descartes who, in a famous passage of the Meditations, points out how a piece of melting wax changes its colour but always retains extension. Extension he therefore regarded as an essential quality of matter, the sensible qualities being due to us or subjective. Locke puts the matter naïvely in the form, that ideas of figure or motion ex actly resemble their original in real things, whereas colour and taste have nothing like themselves in things, and are the work of the mind. As thus drawn, the distinction corresponds to the practice of science and the tradition of the so-called mechanical theory of the world, which has been of such enormous practical value for scientific procedure.
Locke's statement implies that the primary qualities are real and the secondary ones subjective or mental, that is, have no existence apart from the mind; and secondly that the primary qualities are prior in the order of importance and fact to the secondary ones, for the secondary qualities are due to the im pingement, however indirect, upon our sense-organs of the primary qualities of the microscopic constituents of matter. Two funda mental questions are therefore raised for philosophy : the relation of the two sets of qualities in respect of reality; are they un equally real, the one independent of the mind and the other de pendent on the mind ; and secondly their relative status, which of the two is prior in rank in the world of ideas to which they both belong. It is not strange, therefore, that the formulation of the difference between them raises vital questions of philosophy as a whole.