Full Idea
If Simmias is taller than Socrates, they are indirectly related; they are related via their possession of properties that are themselves directly - and internally - related. Hence relational truths are made true by non-relational features of the world.
Gist of Idea
Two people are indirectly related by height; the direct relation is internal, between properties
Source
John Heil (Relations [2009], 'Founding')
Book Reference
'Routledge Companion to Metaphysics', ed/tr. Le Poidevin/Simons etc [Routledge 2012], p.317
A Reaction
This seems to be a strategy for reducing external relations to internal relations, which are intrinsic to objects, which thus reduces the ontology. Heil is not endorsing it, but cites Kit Fine 2000. The germ of this idea is in Plato.
Related Idea
Idea 21347 If Simmias is taller than Socrates, that isn't a feature that is just in Simmias [Plato]