Primary and Secondary Qualities

epistemological concepts of mechanistic materialism. Introduced by the English scientist R. Boyle, the concepts became well known through J. Locke’s Essay Concerning Human Understanding (1690). However, the terms themselves are found in medieval scholasticism, in the work of Albertus Magnus, for example.

Locke defined primary qualities as the objective properties of material bodies: extension, number, figure (shape), solidity, position, qualitative characteristics in general, mechanical motion, rest, and duration (J. Locke, Izbr. filos, proizv., vol. 1, Moscow, 1960, p. 155). According to Locke, the secondary qualities are subjective sensations that do not coincide with the properties of external objects as such. Among the many secondary qualities are color, sound, taste, and smell.

The classification of qualities according to the degree of their objectivity is found as early as the writings of Democritus, who drew a distinction between subjective knowledge “by opinion” (that is, knowledge in the form of sensations) and knowledge “by truth,” or intellectually attained knowledge of the properties of atoms. The teachings of the 17th- and 18th-century philosophers concerning the primary and secondary qualities were directly linked with an atomistic and mechanistic world view. According to Galileo, the only verifiable qualities are those which can be expressed in terms of geometry. Hobbes considered the spatial and temporal qualities of extension and motion to be the only primary qualities. Galileo, Descartes, P. Gassendi, and Hobbes thought that only human reason could discover the primary qualities in objects, whereas Locke believed that “ideas” of primary qualities were acquired directly through the senses. These theories do not differ significantly. They are characterized by general mechanistic principles, such as abstraction from different types of matter and the definition of objective qualities as the measurable, mechanical properties of external objects.

The inability of 17th- and 18th-century philosophy to solve the problem of the objective content of sensations posed by Locke opened the way for a subjective interpretation of primary and secondary qualities. Basically, G. Berkeley rejected the classification of qualities as primary or secondary. He considered all qualities subjective. Interpreting the concept of primary and secondary qualities from the standpoint of agnosticism, D. Hume and I. Kant denied any similarity between sensations and the properties of external objects and transferred the subjective understanding of secondary qualities to primary qualities.

At the end of the 19th century and during the 20th century, these idealistic views were the premise for empiriocritical, neorealist, and neopositivist theories of knowledge. The thought of some metaphysical materialists was characterized by a repudiation of the objective content of secondary qualities and, at the same time, by a recognition of the objectivity of the primary qualities. These philosophers tended to understand the secondary qualities as conventional symbols.

Dialectical materialism rejects the division of the properties of objects into primary and secondary qualities. It regards sensations as subjective images of objective reality, reflecting but not identical to the properties of things.