Kœstler (1979: 535-6, 539):
The division of the world into 'primary' and 'secondary' qualities was completed by Descartes. He further reduced primary qualities to 'extension' and 'motion', which form the 'realm of extension' — res extensa — and he lumped together everything else in the res cogitans, the realm of the mind …
Descartes carried the process one step further [than Galileo] by paring down the reality of the external world to particles whose only quality was extension in space and motion in space and time.
Blogger Comment:
From the perspective of Systemic Functional Linguistic theory, all such qualities, primary and secondary, extension and motion, exist "only in the observer's consciousness" — since they are all meanings construed of experience.
