God and Abraham

Bill argues here that the sentences used to express his notion of 'modes of being', in particular, the notion of existing dependently on another being, as ordinary things may be said to depend on God, cannot be given a Quinean regimentation.

Bill introduces the QuineSpeak predicate letter 'D' to translate the English predicate '---depends for its existence on---'.  So, if 'a' is the QuineSpeak name for Abraham, say, and 'g' for God, then the QuineSpeak wff 'Dag' translates 'Abraham depends for his existence on God'.  The QuineSpeak is no more or less than a compressed version of the English.  Bill then goes on to say

To translate the target sentences into QuineSpeak one has to treat the presumably sui generis relation of existential dependence of creatures on God as if it were an ordinary external relation.  But such ordinary relations presuppose for their obtaining the existence of their relata. 

This is where he loses me.  Why have we moved from talk of predicates into talk of relations? And what extra leverage does Bill find in relations that cannot be found in predicates?

Suppose the world consists of just God and Abraham (and they are distinct).  Then the only truth of the form 'Dxy' is 'Dag'.  All the other sentences of this form, viz,  'Daa', 'Dgg', 'Dga', are false.  Or, in relation talk, the only element in the relation D is (a,g).  And before God created Abraham there was no truth of the form 'Dxy' and the relation D was empty.  Where is the problem with this?