Descartes on the distinction between primary and secondary qualities

ABSTRACT

Descartes did not use the terms ‘primary’ and ‘secondary’ qualities, but a similar distinction emerges from his texts: certain qualities of objects (such as size and shape) are intrinsic properties of matter, whereas others (like colours and smells) are products of the interaction with a perceiver. A common interpretation states that the division between primary and secondary qualities is explained by the way in which we are acquainted with them: an idea of a primary quality is similar to its physical causes, and it is clearly and distinctly perceived by the intellect. An idea of a secondary quality is dissimilar to its physical causes and it is obscurely and confusedly perceived by the senses. This view receives the name of ‘bifurcation reading’ (Simmons, A. ‘Descartes on the Cognitive Structure of Sensory Experience’. Philosophy and Phenomenological Research, LXVII, no. 3 (November 2003)). While it integrates well some textual occurrences, it creates a problematic fragmentation within single acts of perception. This paper contends that this reading is incorrect. It presents several arguments for the claim that the distinction of qualities is due to the different ways in which our ideas of them misrepresent their physical causes. Then, Descartes’ dissimilarity thesis between physical objects and our ideas of them remains a structural feature of his theory of sensory perception and not a local phenomenon affecting only ideas of secondary qualities.