Full Idea
Attributes and classes are said to be distinguished by the fact that whereas no two classes coincide in membership, there are supposed to be distinct but coextensive attributes.
Gist of Idea
While no two classes coincide in membership, there are distinct but coextensive attributes
Source
Richard Cartwright (Classes and Attributes [1967], §2)
Book Reference
Cartwright,Richard: 'Philosophical Essays' [MIT 1987], p.161
A Reaction
This spells out the standard problem of renates and cordates, that creatures with hearts and with kidneys are precisely coextensive, but that these properties are different. Cartwright then attacks the distinction.