Before revision: Hilary Putnam's book Ethics without ontology (Harvard, 2004) argues for a similar view, that ethical (and for that matter mathematical) sentences can be true and objective without there being any objects to make them so.
After revision: Hilary Putnam's book Ethics without Ontology (Harvard, 2004) argues for a similar view, that ethical (and for that matter mathematical) sentences can be true and objective without there being any objects to make them so.