 Primary–secondary quality distinction

In an account of perception, distinguish an object's physical constitution from its powers to produce experiences in perceivers. The distinction between primary qualities and secondary qualities does not by itself prove an external world or imply that dispositions are unreal.^[ref]

The primary–secondary quality distinction is a philosophical concept introduced by the philosopher John Locke in his work "An Essay Concerning Human Understanding." It classifies qualities of objects into two categories: primary qualities and secondary qualities. 1. **Primary Qualities**: These are features that exist in the object itself, independent of any observer. Primary qualities include characteristics such as solidity, extension, motion, number, and figure.