Full Idea
On the conception that properties are powers, it is no longer obvious that causal relations are external relations. Given the powers - all the powers in play - you have the manifestations.
Gist of Idea
If properties are powers, then causal relations are internal relations
Source
John Heil (Relations [2009], 'Causal')
Book Reference
'Routledge Companion to Metaphysics', ed/tr. Le Poidevin/Simons etc [Routledge 2012], p.317
A Reaction
This also delivers on a plate the necessity felt to be in causal relations, because the relation is inevitable once you are given the relata. But can you have an accidental (rather than essential) internal relation? Not in the case of numbers.
Related Idea
Idea 21348 In the case of 5 and 6, their relational truthmaker is just the numbers [Heil]