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Full Idea
Fred Sommers, in his treatment of types, says that two ontological categories cannot overlap; they are either disjoint, or one properly includes the other. This is sometimes referred to as Sommers' Law.
Gist of Idea
Categories can't overlap; they are either disjoint, or inclusive
Source
report of Fred Sommers (Types and Ontology [1963], p.355) by Jan Westerhoff - Ontological Categories §24
Book Ref
Westerhoff,Jan: 'Ontological Categories' [OUP 2005], p.57
A Reaction
The 'types', of course, go back to Bertrand Russell's theory of types, which is important in discussions of ontological categories. Carnap pursued it, trying to derive ontological categories from grammatical categories. 85% agree with Sommers.
| 18904 | 'Predicable' terms come in charged pairs, with one the negation of the other [Sommers, by Engelbretsen] |
| 18903 | Sommers promotes the old idea that negation basically refers to terms [Sommers, by Engelbretsen] |
| 18893 | Translating into quantificational idiom offers no clues as to how ordinary thinkers reason [Sommers] |
| 18894 | Predicates form a hierarchy, from the most general, down to names at the bottom [Sommers] |
| 18901 | Truthmakers are facts 'of' a domain, not something 'in' the domain [Sommers] |
| 18895 | Logic which maps ordinary reasoning must be transparent, and free of variables [Sommers] |
| 18900 | Unfortunately for realists, modern logic cannot say that some fact exists [Sommers] |
| 18898 | In standard logic, names are the only way to refer [Sommers] |
| 18897 | Predicate logic has to spell out that its identity relation '=' is an equivalent relation [Sommers] |
| 13127 | Categories can't overlap; they are either disjoint, or inclusive [Sommers, by Westerhoff] |