Philosophical Works · Chapter
CXCVIII explained
Descartes argues that the senses only perceive figure, magnitude, and motion of external objects, and that all sensations (including light, sound, pain) arise from local motion of the nerves.
What happens
Descartes argues that the senses only perceive figure, magnitude, and motion of external objects, and that all sensations (including light, sound, pain) arise from local motion of the nerves. He concludes that qualities like color, smell, taste, and heat are not in objects themselves but are merely dispositions of objects to move our nerves in various ways.
Free preview opens on this chapter — companions, themes, and character notes appear beside the text.
Narrative arc
Story tension across the book — this chapter sits in Falling action.
- Setup
- Escalation
- Breaking point
- Aftermath
- Closing
This passage marks the story's dramatic climax because it presents the precise moment of epistemological crisi…
Full beat labels and climax notes unlock in the reader.
Follow the arc while readingThemes in this chapter
- Mind-Body Dualism
The chapter distinguishes between the soul's sensations and the purely mechanical motions of the body, reinforcing the dualist separation.
- Reason and Method
Descartes applies a methodical reasoning to deduce that only figure, magnitude, and motion are truly in external objects, rejecting unobservable qualities.
Characters to notice
- Narrator
The narrator presents the argument that sensory qualities are reducible to motion and figure.
- René Descartes
Descartes is the philosopher advancing the mechanistic view of perception.
Key passages
“we in no way likewise apprehend that in external objects, which we call light, colour, smell, taste, sound, heat or cold, and the other tactile qualities, or that which we call their substantial forms, unless as the various dispositions of these objects which have the power of moving our nerves in various ways.”
We do not perceive light, color, smell, taste, sound, heat, cold, or other tactile qualities as they exist in objects; rather, we perceive only the dispositions of objects to move our nerves in different ways.
This summarizes Descartes' conclusion that sensory qualities are not inherent in objects but are effects of motion on the senses.
