Full Idea
It is obvious that a relation which is symmetrical and transitive must be reflexive throughout its domain.
Gist of Idea
If a relation is symmetrical and transitive, it has to be reflexive
Source
Bertrand Russell (Introduction to Mathematical Philosophy [1919], II)
Book Reference
Russell,Bertrand: 'Introduction to Mathematical Philosophy' [George Allen and Unwin 1975], p.16
A Reaction
Compare Idea 13543! The relation will return to its originator via its neighbours, rather than being directly reflexive?
Related Idea
Idea 13543 A relation is not reflexive, just because it is transitive and symmetrical [Bostock]