Descartes' Wax Argument and the Limits of Sense-Perception

Introduction: Descartes and the Thinking Thing

Descartes' philosophy heavily deals with the "thinking thing" — the relationship between perception, knowledge, and what each can reliably tell us about the world. Like Plato's views on knowledge and opinion, Descartes concludes that human perception — or opinion, in Plato's terms — is faulty. However, unlike Plato, who takes sense-perception in stride and allows its use as a stepping stone toward knowledge, Descartes discards sense-perception entirely, determining that it is an unreliable path to true and certain knowledge. In Meditations II, Descartes further develops this argument through his now-famous example of a piece of wax.

The Wax Argument in Meditations II

Prior to his example with the wax, Descartes has logically deduced that he is "a thing which thinks," and that a thinking thing has the inherent ability to "doubt, understand, conceive, deny, will, refuse, and also imagine and feel." In order to affirm his status as a thinking thing, he examines the case of a piece of wax.

In this example, a piece of wax is held near a fire, where it gradually changes shape over time, acquiring a different set of sensory properties. It remains wax — yet Descartes argues that this recognition does not come from one's perception of the wax melting into a different shape. How does one know what shape the wax takes at the end of the process? Descartes argues forcefully that the wax can take on an infinite number of shapes, far more than one's imagination could anticipate. As he writes in Meditations II:

"What then did I know so distinctly in this piece of wax? It could certainly be nothing of all that the senses brought to my notice, since all these things which fall under taste, smell, sight, touch, and hearing, are found to be changed, and yet the same wax remains."