Full Idea
An asymmetric relation must be irreflexive: any case of aRa will yield a reductio of the assumption that R is asymmetric.
Gist of Idea
A reflexive relation entails that the relation can't be asymmetric
Source
Marian David (Truth-making and Correspondence [2009], 4)
Book Reference
'Truth and Truth-Making', ed/tr. Lowe,E.J./Rami,A. [Acumen 2009], p.152